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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
1 of 49
Overview of Complex NetworksPrinciples of Complex Systems
CSYS/MATH 300, Spring, 2013 | #SpringPoCS2013
Prof. Peter Dodds@peterdodds
Department of Mathematics & Statistics | Center for Complex Systems |Vermont Advanced Computing Center | University of Vermont
Licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
2 of 49
Outline
Basic definitions
Examples of Complex Networks
Properties of Complex Networks
Nutshell
References
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
3 of 49
net•work |ˈnetˌwərk|noun
1 an arrangement of intersecting horizontal and vertical lines.
• a complex system of roads, railroads, or other transportation routes :
a network of railroads.
2 a group or system of interconnected people or things : a trade network.
• a group of people who exchange information, contacts, and
experience for professional or social purposes : a support network.
• a group of broadcasting stations that connect for the simultaneous
broadcast of a program : the introduction of a second TV network | [as adj. ]
network television.
• a number of interconnected computers, machines, or operations :
specialized computers that manage multiple outside connections to a network | a
local cellular phone network.
• a system of connected electrical conductors.
verb [ trans. ]
connect as or operate with a network : the stock exchanges have proven to be
resourceful in networking these deals.
• link (machines, esp. computers) to operate interactively : [as adj. ] (
networked) networked workstations.
• [ intrans. ] [often as n. ] ( networking) interact with other people to
exchange information and develop contacts, esp. to further one's
career : the skills of networking, bargaining, and negotiation.
DERIVATIVES
net•work•a•ble adjective
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Thesaurus deliciousness:
networknoun
1 a network of arteries WEB, lattice, net, matrix, mesh,
crisscross, grid, reticulum, reticulation; Anatomy plexus.
2 a network of lanes MAZE, labyrinth, warren, tangle.
3 a network of friends SYSTEM, complex, nexus, web,
webwork.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Ancestry:
From Keith Briggs’s excellent etymologicalinvestigation: ()
I Opus reticulatum:I A Latin origin?
[http://serialconsign.com/2007/11/we-put-net-network]
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
6 of 49
Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
![Page 8: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/8.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
6 of 49
Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
![Page 9: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/9.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
6 of 49
Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
![Page 10: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/10.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
6 of 49
Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
![Page 11: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/11.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
6 of 49
Ancestry:
First known use: Geneva Bible, 1560‘And thou shalt make unto it a grate like networke ofbrass (Exodus xxvii 4).’
From the OED via Briggs:I 1658–: reticulate structures in animalsI 1839–: rivers and canalsI 1869–: railwaysI 1883–: distribution network of electrical cablesI 1914–: wireless broadcasting networks
![Page 12: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/12.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
7 of 49
Ancestry:
Net and Work are venerable old words:I ‘Net’ first used to mean spider web (King Ælfréd, 888).I ‘Work’ appear to have long meant purposeful action.
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 2 of 4http://keithbriggs.info/network.html
gescylde hálgan nette (with a net-work of clouds), Cd. Th. 182, Ii; Exod. 74. [Goth, nati: O. Sax. netti,(fisk-)net: O. Frs. nette: Icel. net; gen. pl. netja : O. H. Ger. nezzi rete.] v. æl-, boge-, breóst-, deór-,drag-, feng-, fisc-, fleóh-, here-, bring-, inwit-, mycg-, searo-, wæl-nett, and next word.
nette, an; f. The net-like caul :-- Nette (under the heading de membris hominum) disceptum i. reticulum (cf. hocreticulum, pinguedo circa jecur [fat around liver], 704, 7), Wülck. Gl. 293,6. Nettae oligia, 35, 34. Nytteobligia [binding, bandage], Wrt. Voc. i. 45, 18. Nette, ii. 63, 39 : disceptum, 26,19. [Icel. netja thecaul: cf. O. H. Ger. nezzi adeps [fat] intestini; pl. intestina.] v. neta.
Net has many cognates in Germanic languages and a probable one in Latin. The Germanic words areof neuter gender (except for nót which is feminine); the Latin word is feminine. Note that the normalLatin word for a net is rete, although there may have also been a Vulgar Latin word *tragina for adragnet.
language word
Gothic nati
OldEnglish
net(t),netti
MiddleEnglish
net
ModernEnglish
net
ModernDutch
net
Old HighGerman
nezzi
MiddleHighGerman
netze
ModernHighGerman
Netz
OldFrisian
nette
OldSaxon
netti
OldNorse
net(netjav.),nót
ModernIcelandic
net
ModernSwedish
nät
Latin nassa
The Gothic word occurs exactly seven times in the bible. It takes the form natja in the dative. BecauseGothic is the earliest record of Germanic (from about 350), it is worth looking at all these occurrences:
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 4 of 4http://keithbriggs.info/network.html
sources
Bosworth, Joseph: (Northcote Toller, T. ed.) An Anglo-Saxon Dictionary. Dictionary, Supplement andAddenda Oxford University Press, 1st ed. n.d., reprinted 1983, 1966, 1972. [Abbreviations: Wrt. Voc. i:T. Wright, A volume of vocabularies, 1857. Quoted by page and number of gloss. Wrt. Voc. ii: T. Wright,A second volume of vocabularies, 1873. Quoted by page and line. Ælfc. Gr: Ælfric's Grammar. Ps. Spl.:Psalterium Davidis Latino-Saxonicum vetus. Lk. Skt.: The gospel according to St. Luke. Mt. Kmbl.: Thegospel according to St. Matthew in Anglo-Saxon and Northumbrian versions. ed. J. M. Kemble. Jn. Skt.:The gospel according to St. John. Som.: Dictionarium Saxonico-Latino-Anglicum, by E. Somner, Oxford1659. Coll. Monast. Th.: Colloquium ad pueros linguae Latinae locutione exercendos ad Ælfricocompilatum. Homl. Th.: The homilies of Ælfric. Wülck. Gl.: Anglo-Saxon and Old English vocabularies,by Thomas Wright, edited by R. P. Wülcker, London 1884. Cd. Th.: Cædmon's metrical paraphrase, byB. Thorpe, London 1832.]
Stamm, Friedrich Ludwig: Friedrich Ludwig Stamm's Ulfilas oder die uns erhaltenen Denkmäler dergotischen Sprache: Text, Wörterbuch und Grammatik Ungekürzte Neuauflage, Nachdruck der Ausgabeaus dem Jahre 1872 [Essen]: Magnus-Verlag, [1984]. ISBN: 3884001655
This page was last modified 2005 Sep 26 (Tuesday) 09:52 by
I ‘Network’ = something built based on the idea ofnatural, flexible lattice or web.
I c.f., ironwork, stonework, fretwork.
![Page 13: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/13.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
7 of 49
Ancestry:
Net and Work are venerable old words:I ‘Net’ first used to mean spider web (King Ælfréd, 888).I ‘Work’ appear to have long meant purposeful action.
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 2 of 4http://keithbriggs.info/network.html
gescylde hálgan nette (with a net-work of clouds), Cd. Th. 182, Ii; Exod. 74. [Goth, nati: O. Sax. netti,(fisk-)net: O. Frs. nette: Icel. net; gen. pl. netja : O. H. Ger. nezzi rete.] v. æl-, boge-, breóst-, deór-,drag-, feng-, fisc-, fleóh-, here-, bring-, inwit-, mycg-, searo-, wæl-nett, and next word.
nette, an; f. The net-like caul :-- Nette (under the heading de membris hominum) disceptum i. reticulum (cf. hocreticulum, pinguedo circa jecur [fat around liver], 704, 7), Wülck. Gl. 293,6. Nettae oligia, 35, 34. Nytteobligia [binding, bandage], Wrt. Voc. i. 45, 18. Nette, ii. 63, 39 : disceptum, 26,19. [Icel. netja thecaul: cf. O. H. Ger. nezzi adeps [fat] intestini; pl. intestina.] v. neta.
Net has many cognates in Germanic languages and a probable one in Latin. The Germanic words areof neuter gender (except for nót which is feminine); the Latin word is feminine. Note that the normalLatin word for a net is rete, although there may have also been a Vulgar Latin word *tragina for adragnet.
language word
Gothic nati
OldEnglish
net(t),netti
MiddleEnglish
net
ModernEnglish
net
ModernDutch
net
Old HighGerman
nezzi
MiddleHighGerman
netze
ModernHighGerman
Netz
OldFrisian
nette
OldSaxon
netti
OldNorse
net(netjav.),nót
ModernIcelandic
net
ModernSwedish
nät
Latin nassa
The Gothic word occurs exactly seven times in the bible. It takes the form natja in the dative. BecauseGothic is the earliest record of Germanic (from about 350), it is worth looking at all these occurrences:
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 4 of 4http://keithbriggs.info/network.html
sources
Bosworth, Joseph: (Northcote Toller, T. ed.) An Anglo-Saxon Dictionary. Dictionary, Supplement andAddenda Oxford University Press, 1st ed. n.d., reprinted 1983, 1966, 1972. [Abbreviations: Wrt. Voc. i:T. Wright, A volume of vocabularies, 1857. Quoted by page and number of gloss. Wrt. Voc. ii: T. Wright,A second volume of vocabularies, 1873. Quoted by page and line. Ælfc. Gr: Ælfric's Grammar. Ps. Spl.:Psalterium Davidis Latino-Saxonicum vetus. Lk. Skt.: The gospel according to St. Luke. Mt. Kmbl.: Thegospel according to St. Matthew in Anglo-Saxon and Northumbrian versions. ed. J. M. Kemble. Jn. Skt.:The gospel according to St. John. Som.: Dictionarium Saxonico-Latino-Anglicum, by E. Somner, Oxford1659. Coll. Monast. Th.: Colloquium ad pueros linguae Latinae locutione exercendos ad Ælfricocompilatum. Homl. Th.: The homilies of Ælfric. Wülck. Gl.: Anglo-Saxon and Old English vocabularies,by Thomas Wright, edited by R. P. Wülcker, London 1884. Cd. Th.: Cædmon's metrical paraphrase, byB. Thorpe, London 1832.]
Stamm, Friedrich Ludwig: Friedrich Ludwig Stamm's Ulfilas oder die uns erhaltenen Denkmäler dergotischen Sprache: Text, Wörterbuch und Grammatik Ungekürzte Neuauflage, Nachdruck der Ausgabeaus dem Jahre 1872 [Essen]: Magnus-Verlag, [1984]. ISBN: 3884001655
This page was last modified 2005 Sep 26 (Tuesday) 09:52 by
I ‘Network’ = something built based on the idea ofnatural, flexible lattice or web.
I c.f., ironwork, stonework, fretwork.
![Page 14: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/14.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
7 of 49
Ancestry:
Net and Work are venerable old words:I ‘Net’ first used to mean spider web (King Ælfréd, 888).I ‘Work’ appear to have long meant purposeful action.
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 2 of 4http://keithbriggs.info/network.html
gescylde hálgan nette (with a net-work of clouds), Cd. Th. 182, Ii; Exod. 74. [Goth, nati: O. Sax. netti,(fisk-)net: O. Frs. nette: Icel. net; gen. pl. netja : O. H. Ger. nezzi rete.] v. æl-, boge-, breóst-, deór-,drag-, feng-, fisc-, fleóh-, here-, bring-, inwit-, mycg-, searo-, wæl-nett, and next word.
nette, an; f. The net-like caul :-- Nette (under the heading de membris hominum) disceptum i. reticulum (cf. hocreticulum, pinguedo circa jecur [fat around liver], 704, 7), Wülck. Gl. 293,6. Nettae oligia, 35, 34. Nytteobligia [binding, bandage], Wrt. Voc. i. 45, 18. Nette, ii. 63, 39 : disceptum, 26,19. [Icel. netja thecaul: cf. O. H. Ger. nezzi adeps [fat] intestini; pl. intestina.] v. neta.
Net has many cognates in Germanic languages and a probable one in Latin. The Germanic words areof neuter gender (except for nót which is feminine); the Latin word is feminine. Note that the normalLatin word for a net is rete, although there may have also been a Vulgar Latin word *tragina for adragnet.
language word
Gothic nati
OldEnglish
net(t),netti
MiddleEnglish
net
ModernEnglish
net
ModernDutch
net
Old HighGerman
nezzi
MiddleHighGerman
netze
ModernHighGerman
Netz
OldFrisian
nette
OldSaxon
netti
OldNorse
net(netjav.),nót
ModernIcelandic
net
ModernSwedish
nät
Latin nassa
The Gothic word occurs exactly seven times in the bible. It takes the form natja in the dative. BecauseGothic is the earliest record of Germanic (from about 350), it is worth looking at all these occurrences:
6/6/09 9:45 PMKeith Briggs: : Etymology of `network'
Page 4 of 4http://keithbriggs.info/network.html
sources
Bosworth, Joseph: (Northcote Toller, T. ed.) An Anglo-Saxon Dictionary. Dictionary, Supplement andAddenda Oxford University Press, 1st ed. n.d., reprinted 1983, 1966, 1972. [Abbreviations: Wrt. Voc. i:T. Wright, A volume of vocabularies, 1857. Quoted by page and number of gloss. Wrt. Voc. ii: T. Wright,A second volume of vocabularies, 1873. Quoted by page and line. Ælfc. Gr: Ælfric's Grammar. Ps. Spl.:Psalterium Davidis Latino-Saxonicum vetus. Lk. Skt.: The gospel according to St. Luke. Mt. Kmbl.: Thegospel according to St. Matthew in Anglo-Saxon and Northumbrian versions. ed. J. M. Kemble. Jn. Skt.:The gospel according to St. John. Som.: Dictionarium Saxonico-Latino-Anglicum, by E. Somner, Oxford1659. Coll. Monast. Th.: Colloquium ad pueros linguae Latinae locutione exercendos ad Ælfricocompilatum. Homl. Th.: The homilies of Ælfric. Wülck. Gl.: Anglo-Saxon and Old English vocabularies,by Thomas Wright, edited by R. P. Wülcker, London 1884. Cd. Th.: Cædmon's metrical paraphrase, byB. Thorpe, London 1832.]
Stamm, Friedrich Ludwig: Friedrich Ludwig Stamm's Ulfilas oder die uns erhaltenen Denkmäler dergotischen Sprache: Text, Wörterbuch und Grammatik Ungekürzte Neuauflage, Nachdruck der Ausgabeaus dem Jahre 1872 [Essen]: Magnus-Verlag, [1984]. ISBN: 3884001655
This page was last modified 2005 Sep 26 (Tuesday) 09:52 by
I ‘Network’ = something built based on the idea ofnatural, flexible lattice or web.
I c.f., ironwork, stonework, fretwork.
![Page 15: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/15.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
![Page 16: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/16.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
![Page 17: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/17.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
![Page 18: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/18.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
![Page 19: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/19.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
![Page 20: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/20.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
I Piranha physicus
I Hunt in packs.
I Feast on new and interesting ideas(see chaos, cellular automata, ...)
![Page 21: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/21.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
I Piranha physicus
I Hunt in packs.
I Feast on new and interesting ideas(see chaos, cellular automata, ...)
![Page 22: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/22.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
8 of 49
Key Observation:
I Many complex systemscan be viewed as complex networksof physical or abstract interactions.
I Opens door to mathematical and numerical analysis.I Dominant approach of last decade of a
theoretical-physics/stat-mechish flavor.I Mindboggling amount of work published on complex
networks since 1998...I ... largely due to your typical theoretical physicist:
I Piranha physicus
I Hunt in packs.
I Feast on new and interesting ideas(see chaos, cellular automata, ...)
![Page 23: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/23.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
9 of 49
Popularity (according to Google Scholar)
“Collective dynamics of ‘small-world’ networks” [18]
I Watts and StrogatzNature, 1998
I Cited ≈ 18,450 times (as of March 18, 2013)
“Emergence of scaling in random networks” [2]
I Barabási and AlbertScience, 1999
I Cited ≈ 16,050 times (as of March 18, 2013)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
10 of 49
Popularity (according to Google Scholar)
Review articles:I S. Boccaletti et al.
“Complex networks: structure and dynamics” [3]
Times cited: 3,500 (as of March 18, 2013)
I M. Newman“The structure and function of complex networks” [13]
Times cited: 9,100 (as of March 18, 2013)
I R. Albert and A.-L. Barabási“Statistical mechanics of complex networks” [1]
Times cited: 11,600 (as of March 18, 2013)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Popularity according to textbooks:
Textbooks:I Mark Newman (Physics, Michigan)
“Networks: An Introduction” ()I David Easley and Jon Kleinberg (Economics and
Computer Science, Cornell)“Networks, Crowds, and Markets: Reasoning About aHighly Connected World” ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Popularity according to textbooks:
Textbooks:I Mark Newman (Physics, Michigan)
“Networks: An Introduction” ()I David Easley and Jon Kleinberg (Economics and
Computer Science, Cornell)“Networks, Crowds, and Markets: Reasoning About aHighly Connected World” ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Popularity according to books:
The Tipping Point: How Little Things canmake a Big Difference—Malcolm Gladwell [8]
Nexus: Small Worlds and the GroundbreakingScience of Networks—Mark Buchanan
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
13 of 49
Popularity according to books:
Linked: How Everything Is Connected toEverything Else and What ItMeans—Albert-Laszlo Barabási
Six Degrees: The Science of a ConnectedAge—Duncan Watts [17]
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Numerous others . . .
I Complex Social Networks—F. Vega-Redondo [16]
I Fractal River Basins: Chance and Self-Organization—I.Rodríguez-Iturbe and A. Rinaldo [14]
I Random Graph Dynamics—R. Durette
I Scale-Free Networks—Guido Caldarelli
I Evolution and Structure of the Internet: A StatisticalPhysics Approach—Romu Pastor-Satorras andAlessandro Vespignani
I Complex Graphs and Networks—Fan Chung
I Social Network Analysis—Stanley Wasserman andKathleen Faust
I Handbook of Graphs and Networks—Eds: StefanBornholdt and H. G. Schuster [5]
I Evolution of Networks—S. N. Dorogovtsev and J. F. F.Mendes [7]
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.
∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
15 of 49
More observations
I But surely networks aren’t new...I Graph theory is well established...I Study of social networks started in the 1930’s...I So why all this ‘new’ research on networks?I Answer: Oodles of Easily Accessible Data.I We can now inform (alas) our theories
with a much more measurable reality.∗
I A worthy goal: establish mechanistic explanations.∗If this is upsetting, maybe string theory is for you...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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More observations
I Web-scale data sets can be overly exciting.
Witness:I The End of Theory: The Data Deluge Makes the
Scientific Theory Obsolete (Anderson, Wired) ()I “The Unreasonable Effectiveness of Data,”
Halevy et al. [9].I c.f. Wigner’s “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences” [19]
But:I For scientists, description is only part of the battle.I We still need to understand.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
16 of 49
More observations
I Web-scale data sets can be overly exciting.
Witness:I The End of Theory: The Data Deluge Makes the
Scientific Theory Obsolete (Anderson, Wired) ()I “The Unreasonable Effectiveness of Data,”
Halevy et al. [9].I c.f. Wigner’s “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences” [19]
But:I For scientists, description is only part of the battle.I We still need to understand.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
16 of 49
More observations
I Web-scale data sets can be overly exciting.
Witness:I The End of Theory: The Data Deluge Makes the
Scientific Theory Obsolete (Anderson, Wired) ()I “The Unreasonable Effectiveness of Data,”
Halevy et al. [9].I c.f. Wigner’s “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences” [19]
But:I For scientists, description is only part of the battle.I We still need to understand.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
16 of 49
More observations
I Web-scale data sets can be overly exciting.
Witness:I The End of Theory: The Data Deluge Makes the
Scientific Theory Obsolete (Anderson, Wired) ()I “The Unreasonable Effectiveness of Data,”
Halevy et al. [9].I c.f. Wigner’s “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences” [19]
But:I For scientists, description is only part of the battle.I We still need to understand.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
16 of 49
More observations
I Web-scale data sets can be overly exciting.
Witness:I The End of Theory: The Data Deluge Makes the
Scientific Theory Obsolete (Anderson, Wired) ()I “The Unreasonable Effectiveness of Data,”
Halevy et al. [9].I c.f. Wigner’s “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences” [19]
But:I For scientists, description is only part of the battle.I We still need to understand.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
17 of 49
Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
17 of 49
Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
17 of 49
Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
17 of 49
Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
17 of 49
Super Basic definitions
Nodes = A collection of entities which haveproperties that are somehow related to each otherI e.g., people, forks in rivers, proteins, webpages,
organisms,...
Links = Connections between nodesI Links may be directed or undirected.I Links may be binary or weighted.
Other spiffing words: vertices and edges.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)
I Connection between number of edges m andaverage degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
18 of 49
Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)
I Connection between number of edges m andaverage degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
18 of 49
Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)
I Connection between number of edges m andaverage degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
18 of 49
Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)
I Connection between number of edges m andaverage degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
18 of 49
Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)I Connection between number of edges m and
average degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
18 of 49
Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)I Connection between number of edges m and
average degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Super Basic definitions
Node degree = Number of links per nodeI Notation: Node i ’s degree = ki .I ki = 0,1,2,. . . .I Notation: the average degree of a network = 〈k〉
(and sometimes z)I Connection between number of edges m and
average degree:
〈k〉 = 2mN
.
I Defn: Ni = the set of i ’s ki neighbors
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Super Basic definitions
Adjacency matrix:I We represent a directed network by a matrix A with
link weight aij for nodes i and j in entry (i , j).I e.g.,
A =
0 1 1 1 00 0 1 0 11 0 0 0 00 1 0 0 10 1 0 1 0
I (n.b., for numerical work, we always use sparse
matrices.)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Super Basic definitions
Adjacency matrix:I We represent a directed network by a matrix A with
link weight aij for nodes i and j in entry (i , j).I e.g.,
A =
0 1 1 1 00 0 1 0 11 0 0 0 00 1 0 0 10 1 0 1 0
I (n.b., for numerical work, we always use sparse
matrices.)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
19 of 49
Super Basic definitions
Adjacency matrix:I We represent a directed network by a matrix A with
link weight aij for nodes i and j in entry (i , j).I e.g.,
A =
0 1 1 1 00 0 1 0 11 0 0 0 00 1 0 0 10 1 0 1 0
I (n.b., for numerical work, we always use sparse
matrices.)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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Examples
So what passes for a complex network?I Complex networks are large (in node number)I Complex networks are sparse (low edge to node
ratio)I Complex networks are usually dynamic and evolvingI Complex networks can be social, economic, natural,
informational, abstract, ...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
20 of 49
Examples
So what passes for a complex network?I Complex networks are large (in node number)I Complex networks are sparse (low edge to node
ratio)I Complex networks are usually dynamic and evolvingI Complex networks can be social, economic, natural,
informational, abstract, ...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
20 of 49
Examples
So what passes for a complex network?I Complex networks are large (in node number)I Complex networks are sparse (low edge to node
ratio)I Complex networks are usually dynamic and evolvingI Complex networks can be social, economic, natural,
informational, abstract, ...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
20 of 49
Examples
So what passes for a complex network?I Complex networks are large (in node number)I Complex networks are sparse (low edge to node
ratio)I Complex networks are usually dynamic and evolvingI Complex networks can be social, economic, natural,
informational, abstract, ...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
20 of 49
Examples
So what passes for a complex network?I Complex networks are large (in node number)I Complex networks are sparse (low edge to node
ratio)I Complex networks are usually dynamic and evolvingI Complex networks can be social, economic, natural,
informational, abstract, ...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
21 of 49
Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
21 of 49
Examples
Physical networks
I River networksI Neural networksI Trees and leavesI Blood networks
I The InternetI Road networksI Power grids
I Distribution (branching) versus redistribution(cyclical)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
22 of 49
Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Interaction networksI The BlogosphereI Biochemical
networksI Gene-protein
networksI Food webs: who
eats whomI The World Wide
Web (?)I Airline networksI Call networks
(AT&T)I The Media
datamining.typepad.com ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
23 of 49
Examples
Interaction networks:social networksI SnoggingI FriendshipsI AcquaintancesI Boards and
directorsI OrganizationsI facebook ()
twitter (), (Bearman et al., 2004)
I ‘Remotely sensed’ by: email activity, instantmessaging, phone logs (*cough*).
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Examples
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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ExamplesRelational networksI Consumer purchases
(Wal-Mart: ≈ 1 petabyte = 1015 bytes)
I Thesauri: Networks of words generated by meaningsI Knowledge/Databases/IdeasI Metadata—Tagging: bit.ly () flickr ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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ExamplesRelational networksI Consumer purchases
(Wal-Mart: ≈ 1 petabyte = 1015 bytes)I Thesauri: Networks of words generated by meaningsI Knowledge/Databases/IdeasI Metadata—Tagging: bit.ly () flickr ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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ExamplesRelational networksI Consumer purchases
(Wal-Mart: ≈ 1 petabyte = 1015 bytes)I Thesauri: Networks of words generated by meaningsI Knowledge/Databases/IdeasI Metadata—Tagging: bit.ly () flickr ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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ExamplesRelational networksI Consumer purchases
(Wal-Mart: ≈ 1 petabyte = 1015 bytes)I Thesauri: Networks of words generated by meaningsI Knowledge/Databases/IdeasI Metadata—Tagging: bit.ly () flickr ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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ExamplesRelational networksI Consumer purchases
(Wal-Mart: ≈ 1 petabyte = 1015 bytes)I Thesauri: Networks of words generated by meaningsI Knowledge/Databases/IdeasI Metadata—Tagging: bit.ly () flickr ()
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user notesNov ‘06
all the knoweldge- Penfoldio
facts- mmayes
I would not survive without Wikipedia, it knowseverything, and I want to learn everything.
- RobRemi
The internet encyclopedia- limannka
The mother of all wikis- Username314
Wikipedia- lancepickens
ALWAYS useful!- AmritS
Free Online Encyclopedia, User contributed articles- Maluvia
Welcome to Wikipedia, the free encyclopedia thatanyone can edit.
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The Free Encyclopedia- puffseeker
Very good encycolopedia- slams
Knowledge- neilbriody
Miscellaneous Info- sahing
free online encyclopedia
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Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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Clickworthy Science:
Bollen et al. [4]; a higher resolution figure is here ()
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
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A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
I And even when renderings somehow look good:
“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
I And even when renderings somehow look good:
“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
![Page 97: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/97.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
⇐ Typical hairball
I number of nodes N = 500
I number of edges m = 1000
I average degree 〈k〉 = 4
I And even when renderings somehow look good:
“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
![Page 98: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/98.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
27 of 49
A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
⇐ Typical hairball
I number of nodes N = 500
I number of edges m = 1000
I average degree 〈k〉 = 4
I And even when renderings somehow look good:
“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
![Page 99: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/99.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
27 of 49
A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
⇐ Typical hairball
I number of nodes N = 500
I number of edges m = 1000
I average degree 〈k〉 = 4
I And even when renderings somehow look good:“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
![Page 100: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/100.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
27 of 49
A notable feature of large-scale networks:I Graphical renderings are often just a big mess.
⇐ Typical hairball
I number of nodes N = 500
I number of edges m = 1000
I average degree 〈k〉 = 4
I And even when renderings somehow look good:“That is a very graphic analogy which aidsunderstanding wonderfully while being, strictlyspeaking, wrong in every possible way”said Ponder [Stibbons] —Making Money, T. Pratchett.
I We need to extract digestible, meaningful aspects.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Properties
Some key aspects of real complex networks:
I degreedistribution∗
I assortativityI homophilyI clusteringI motifsI modularity
I concurrencyI hierarchical
scalingI network distancesI centralityI efficiencyI robustness
I Plus coevolution of network structureand processes on networks.∗ Degree distribution is the elephant in the room that
we are now all very aware of...
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
![Page 107: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/107.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
![Page 108: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/108.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
29 of 49
Properties
1. degree distribution Pk
I Pk is the probability that a randomly selected nodehas degree k .
I k = node degree = number of connections.I ex 1: Erdos-Rényi random networks have Poisson
degree distributions:Insert question from assignment 5 ()
Pk = e−〈k〉〈k〉k
k !
I ex 2: “Scale-free” networks: Pk ∝ k−γ ⇒ ‘hubs’.I link cost controls skew.I hubs may facilitate or impede contagion.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Properties
Note:I Erdos-Rényi random networks are a mathematical
construct .I ‘Scale-free’ networks are growing networks that form
according to a plausible mechanism.I Randomness is out there, just not to the degree of a
completely random network.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
30 of 49
Properties
Note:I Erdos-Rényi random networks are a mathematical
construct .I ‘Scale-free’ networks are growing networks that form
according to a plausible mechanism.I Randomness is out there, just not to the degree of a
completely random network.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
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Properties
Note:I Erdos-Rényi random networks are a mathematical
construct .I ‘Scale-free’ networks are growing networks that form
according to a plausible mechanism.I Randomness is out there, just not to the degree of a
completely random network.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.
Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.
Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 113: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/113.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.
Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.
Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 114: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/114.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.
Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.
Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 115: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/115.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.
Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.
Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 116: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/116.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.
Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 117: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/117.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
31 of 49
Properties
2. Assortativity/3. Homophily:I Social networks: Homophily () = birds of a featherI e.g., degree is standard property for sorting:
measure degree-degree correlations.I Assortative network: [12] similar degree nodes
connecting to each other.Often social: company directors, coauthors, actors.
I Disassortative network: high degree nodesconnecting to low degree nodes.Often techological or biological: Internet, WWW,protein interactions, neural networks, food webs.
![Page 118: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/118.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
32 of 49
Local socialness:
4. Clustering:
I Your friends tend to knoweach other.
I Two measures (explained onfollowing slides):
1. Watts & Strogatz [18]
C1 =
⟨∑j1 j2∈Ni
aj1 j2
ki(ki − 1)/2
⟩i
2. Newman [13]
C2 =3×#triangles
#triples
![Page 119: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/119.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
32 of 49
Local socialness:
4. Clustering:
I Your friends tend to knoweach other.
I Two measures (explained onfollowing slides):
1. Watts & Strogatz [18]
C1 =
⟨∑j1 j2∈Ni
aj1 j2
ki(ki − 1)/2
⟩i
2. Newman [13]
C2 =3×#triangles
#triples
![Page 120: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/120.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
32 of 49
Local socialness:
4. Clustering:
I Your friends tend to knoweach other.
I Two measures (explained onfollowing slides):
1. Watts & Strogatz [18]
C1 =
⟨∑j1 j2∈Ni
aj1 j2
ki(ki − 1)/2
⟩i
2. Newman [13]
C2 =3×#triangles
#triples
![Page 121: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/121.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
33 of 49
Example network:
Calculation of C1:
I C1 is the average fraction ofpairs of neighbors who areconnected.
I Fraction of pairs of neighborswho are connected is∑
j1j2∈Niaj1j2
ki(ki − 1)/2
where ki is node i ’s degree,and Ni is the set of i ’sneighbors.
I Averaging over all nodes, wehave:C1 = 1
n∑n
i=1
∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
=⟨∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
⟩i
![Page 122: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/122.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
33 of 49
Example network:
Calculation of C1:
I C1 is the average fraction ofpairs of neighbors who areconnected.
I Fraction of pairs of neighborswho are connected is∑
j1j2∈Niaj1j2
ki(ki − 1)/2
where ki is node i ’s degree,and Ni is the set of i ’sneighbors.
I Averaging over all nodes, wehave:C1 = 1
n∑n
i=1
∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
=⟨∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
⟩i
![Page 123: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/123.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
33 of 49
Example network:
Calculation of C1:
I C1 is the average fraction ofpairs of neighbors who areconnected.
I Fraction of pairs of neighborswho are connected is∑
j1j2∈Niaj1j2
ki(ki − 1)/2
where ki is node i ’s degree,and Ni is the set of i ’sneighbors.
I Averaging over all nodes, wehave:C1 = 1
n∑n
i=1
∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
=⟨∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
⟩i
![Page 124: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/124.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
33 of 49
Example network:
Calculation of C1:
I C1 is the average fraction ofpairs of neighbors who areconnected.
I Fraction of pairs of neighborswho are connected is∑
j1j2∈Niaj1j2
ki(ki − 1)/2
where ki is node i ’s degree,and Ni is the set of i ’sneighbors.
I Averaging over all nodes, wehave:C1 = 1
n∑n
i=1
∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
=⟨∑j1 j2∈Ni
aj1 j2ki (ki−1)/2
⟩i
![Page 125: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/125.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
33 of 49
Example network:
Calculation of C1:
I C1 is the average fraction ofpairs of neighbors who areconnected.
I Fraction of pairs of neighborswho are connected is∑
j1j2∈Niaj1j2
ki(ki − 1)/2
where ki is node i ’s degree,and Ni is the set of i ’sneighbors.
I Averaging over all nodes, wehave:C1 = 1
n∑n
i=1
∑j1 j2∈Ni
aj1 j2ki (ki−1)/2 =⟨∑
j1 j2∈Niaj1 j2
ki (ki−1)/2
⟩i
![Page 126: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/126.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
34 of 49
Triples and triangles
Example network:
Triangles:
Triples:
I Nodes i1, i2, and i3 form a triplearound i1 if i1 is connected to i2and i3.
I Nodes i1, i2, and i3 form atriangle if each pair of nodes isconnected
I The definition C2 = 3×#triangles#triples
measures the fraction of closedtriples
I The ‘3’ appears because foreach triangle, we have 3 closedtriples.
I Social Network Analysis (SNA):fraction of transitive triples.
![Page 127: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/127.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
34 of 49
Triples and triangles
Example network:
Triangles:
Triples:
I Nodes i1, i2, and i3 form a triplearound i1 if i1 is connected to i2and i3.
I Nodes i1, i2, and i3 form atriangle if each pair of nodes isconnected
I The definition C2 = 3×#triangles#triples
measures the fraction of closedtriples
I The ‘3’ appears because foreach triangle, we have 3 closedtriples.
I Social Network Analysis (SNA):fraction of transitive triples.
![Page 128: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/128.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
34 of 49
Triples and triangles
Example network:
Triangles:
Triples:
I Nodes i1, i2, and i3 form a triplearound i1 if i1 is connected to i2and i3.
I Nodes i1, i2, and i3 form atriangle if each pair of nodes isconnected
I The definition C2 = 3×#triangles#triples
measures the fraction of closedtriples
I The ‘3’ appears because foreach triangle, we have 3 closedtriples.
I Social Network Analysis (SNA):fraction of transitive triples.
![Page 129: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/129.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
34 of 49
Triples and triangles
Example network:
Triangles:
Triples:
I Nodes i1, i2, and i3 form a triplearound i1 if i1 is connected to i2and i3.
I Nodes i1, i2, and i3 form atriangle if each pair of nodes isconnected
I The definition C2 = 3×#triangles#triples
measures the fraction of closedtriples
I The ‘3’ appears because foreach triangle, we have 3 closedtriples.
I Social Network Analysis (SNA):fraction of transitive triples.
![Page 130: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/130.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
34 of 49
Triples and triangles
Example network:
Triangles:
Triples:
I Nodes i1, i2, and i3 form a triplearound i1 if i1 is connected to i2and i3.
I Nodes i1, i2, and i3 form atriangle if each pair of nodes isconnected
I The definition C2 = 3×#triangles#triples
measures the fraction of closedtriples
I The ‘3’ appears because foreach triangle, we have 3 closedtriples.
I Social Network Analysis (SNA):fraction of transitive triples.
![Page 131: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/131.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 132: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/132.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 133: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/133.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 134: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/134.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 135: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/135.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 136: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/136.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 137: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/137.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
35 of 49
Clustering:
Sneaky counting for undirected, unweightednetworks:I If the path i–j–` exists then aijaj` = 1.I Otherwise, aijaj` = 0.I We want i 6= ` for good triples.I In general, a path of n edges between nodes i1 and
in travelling through nodes i2, i3, . . . in−1 exists ⇐⇒ai1i2ai2i3ai3i4 · · · ain−2in−1ain−1in = 1.
I
#triples =12
(N∑
i=1
N∑`=1
[A2]
i`− TrA2
)I
#triangles =16
TrA3
![Page 138: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/138.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
36 of 49
Properties
I For sparse networks, C1 tends to discount highlyconnected nodes.
I C2 is a useful and often preferred variantI In general, C1 6= C2.I C1 is a global average of a local ratio.I C2 is a ratio of two global quantities.
![Page 139: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/139.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
36 of 49
Properties
I For sparse networks, C1 tends to discount highlyconnected nodes.
I C2 is a useful and often preferred variantI In general, C1 6= C2.I C1 is a global average of a local ratio.I C2 is a ratio of two global quantities.
![Page 140: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/140.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
36 of 49
Properties
I For sparse networks, C1 tends to discount highlyconnected nodes.
I C2 is a useful and often preferred variantI In general, C1 6= C2.I C1 is a global average of a local ratio.I C2 is a ratio of two global quantities.
![Page 141: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/141.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
36 of 49
Properties
I For sparse networks, C1 tends to discount highlyconnected nodes.
I C2 is a useful and often preferred variantI In general, C1 6= C2.I C1 is a global average of a local ratio.I C2 is a ratio of two global quantities.
![Page 142: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/142.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
36 of 49
Properties
I For sparse networks, C1 tends to discount highlyconnected nodes.
I C2 is a useful and often preferred variantI In general, C1 6= C2.I C1 is a global average of a local ratio.I C2 is a ratio of two global quantities.
![Page 143: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/143.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
37 of 49
Properties
5. motifs:I small, recurring functional subnetworksI e.g., Feed Forward Loop:
Shen-Orr, Uri Alon, et al. [15]
![Page 144: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/144.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
37 of 49
Properties
5. motifs:I small, recurring functional subnetworksI e.g., Feed Forward Loop:
Shen-Orr, Uri Alon, et al. [15]
![Page 145: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/145.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
37 of 49
Properties
5. motifs:I small, recurring functional subnetworksI e.g., Feed Forward Loop:
Shen-Orr, Uri Alon, et al. [15]
![Page 146: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/146.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
38 of 49
Properties
6. modularity and structure/community detection:
Clauset et al., 2006 [6]: NCAA football
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
39 of 49
Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
![Page 148: Overview of Complex Networks - Principles of Complex](https://reader031.vdocument.in/reader031/viewer/2022012011/61d9b25b73797369c4149521/html5/thumbnails/148.jpg)
Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
Nutshell
References
39 of 49
Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Examples ofComplex Networks
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Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Examples ofComplex Networks
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Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Overview ofComplex Networks
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Examples ofComplex Networks
Properties ofComplex Networks
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Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Overview ofComplex Networks
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Examples ofComplex Networks
Properties ofComplex Networks
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Properties
7. concurrency:I transmission of a contagious element only occurs
during contactI rather obvious but easily missed in a simple modelI dynamic property—static networks are not enoughI knowledge of previous contacts crucialI beware cumulated network dataI Kretzschmar and Morris, 1996 [11]
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Examples ofComplex Networks
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Properties
8. Horton-Strahler ratios:I Metrics for branching networks:
I Method for ordering streams hierarchicallyI Number: Rn = Nω/Nω+1I Segment length: Rl = 〈lω+1〉/〈lω〉I Area/Volume: Ra = 〈aω+1〉/〈aω〉
(a) (b) (c)
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Overview ofComplex Networks
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Properties
8. Horton-Strahler ratios:I Metrics for branching networks:
I Method for ordering streams hierarchicallyI Number: Rn = Nω/Nω+1I Segment length: Rl = 〈lω+1〉/〈lω〉I Area/Volume: Ra = 〈aω+1〉/〈aω〉
(a) (b) (c)
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Overview ofComplex Networks
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Examples ofComplex Networks
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Properties
8. Horton-Strahler ratios:I Metrics for branching networks:
I Method for ordering streams hierarchicallyI Number: Rn = Nω/Nω+1I Segment length: Rl = 〈lω+1〉/〈lω〉I Area/Volume: Ra = 〈aω+1〉/〈aω〉
(a) (b) (c)
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
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Properties
8. Horton-Strahler ratios:I Metrics for branching networks:
I Method for ordering streams hierarchicallyI Number: Rn = Nω/Nω+1I Segment length: Rl = 〈lω+1〉/〈lω〉I Area/Volume: Ra = 〈aω+1〉/〈aω〉
(a) (b) (c)
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Overview ofComplex Networks
Basic definitions
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Properties
8. Horton-Strahler ratios:I Metrics for branching networks:
I Method for ordering streams hierarchicallyI Number: Rn = Nω/Nω+1I Segment length: Rl = 〈lω+1〉/〈lω〉I Area/Volume: Ra = 〈aω+1〉/〈aω〉
(a) (b) (c)
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Overview ofComplex Networks
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Examples ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Examples ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
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Properties
9. network distances:
(a) shortest path length dij :I Fewest number of steps between nodes i and j .I (Also called the chemical distance between i and j .)
(b) average path length 〈dij〉:I Average shortest path length in whole network.I Good algorithms exist for calculation.I Weighted links can be accommodated.
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Overview ofComplex Networks
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Examples ofComplex Networks
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Properties
9. network distances:I network diameter dmax:
Maximum shortest path length between any twonodes.
I closeness dcl = [∑
ij d −1ij /
(n2
)]−1:
Average ‘distance’ between any two nodes.I Closeness handles disconnected networks (dij =∞)I dcl =∞ only when all nodes are isolated.I Closeness perhaps compresses too much into one
number
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Overview ofComplex Networks
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Examples ofComplex Networks
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Properties
9. network distances:I network diameter dmax:
Maximum shortest path length between any twonodes.
I closeness dcl = [∑
ij d −1ij /
(n2
)]−1:
Average ‘distance’ between any two nodes.I Closeness handles disconnected networks (dij =∞)I dcl =∞ only when all nodes are isolated.I Closeness perhaps compresses too much into one
number
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Overview ofComplex Networks
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Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:I network diameter dmax:
Maximum shortest path length between any twonodes.
I closeness dcl = [∑
ij d −1ij /
(n2
)]−1:
Average ‘distance’ between any two nodes.I Closeness handles disconnected networks (dij =∞)I dcl =∞ only when all nodes are isolated.I Closeness perhaps compresses too much into one
number
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
9. network distances:I network diameter dmax:
Maximum shortest path length between any twonodes.
I closeness dcl = [∑
ij d −1ij /
(n2
)]−1:
Average ‘distance’ between any two nodes.I Closeness handles disconnected networks (dij =∞)I dcl =∞ only when all nodes are isolated.I Closeness perhaps compresses too much into one
number
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Overview ofComplex Networks
Basic definitions
Examples ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Overview ofComplex Networks
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Properties ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Overview ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Overview ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Overview ofComplex Networks
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Properties
10. centrality:I Many such measures of a node’s ‘importance.’I ex 1: Degree centrality: ki .I ex 2: Node i ’s betweenness
= fraction of shortest paths that pass through i .I ex 3: Edge `’s betweenness
= fraction of shortest paths that travel along `.I ex 4: Recursive centrality: Hubs and Authorities (Jon
Kleinberg [10])
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Nutshell:
Overview Key Points:I The field of complex networks came into existence in
the late 1990s.I Explosion of papers and interest since 1998/99.I Hardened up much thinking about complex systems.I Specific focus on networks that are large-scale,
sparse, natural or man-made, evolving and dynamic,and (crucially) measurable.
I Three main (blurred) categories:1. Physical (e.g., river networks),2. Interactional (e.g., social networks),3. Abstract (e.g., thesauri).
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Nutshell:
Overview Key Points:I The field of complex networks came into existence in
the late 1990s.I Explosion of papers and interest since 1998/99.I Hardened up much thinking about complex systems.I Specific focus on networks that are large-scale,
sparse, natural or man-made, evolving and dynamic,and (crucially) measurable.
I Three main (blurred) categories:1. Physical (e.g., river networks),2. Interactional (e.g., social networks),3. Abstract (e.g., thesauri).
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Examples ofComplex Networks
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Nutshell:
Overview Key Points:I The field of complex networks came into existence in
the late 1990s.I Explosion of papers and interest since 1998/99.I Hardened up much thinking about complex systems.I Specific focus on networks that are large-scale,
sparse, natural or man-made, evolving and dynamic,and (crucially) measurable.
I Three main (blurred) categories:1. Physical (e.g., river networks),2. Interactional (e.g., social networks),3. Abstract (e.g., thesauri).
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Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Nutshell:
Overview Key Points:I The field of complex networks came into existence in
the late 1990s.I Explosion of papers and interest since 1998/99.I Hardened up much thinking about complex systems.I Specific focus on networks that are large-scale,
sparse, natural or man-made, evolving and dynamic,and (crucially) measurable.
I Three main (blurred) categories:1. Physical (e.g., river networks),2. Interactional (e.g., social networks),3. Abstract (e.g., thesauri).
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Basic definitions
Examples ofComplex Networks
Properties ofComplex Networks
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Nutshell:
Overview Key Points:I The field of complex networks came into existence in
the late 1990s.I Explosion of papers and interest since 1998/99.I Hardened up much thinking about complex systems.I Specific focus on networks that are large-scale,
sparse, natural or man-made, evolving and dynamic,and (crucially) measurable.
I Three main (blurred) categories:1. Physical (e.g., river networks),2. Interactional (e.g., social networks),3. Abstract (e.g., thesauri).
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References I
[1] R. Albert and A.-L. Barabási.Statistical mechanics of complex networks.Rev. Mod. Phys., 74:47–97, 2002. pdf ()
[2] A.-L. Barabási and R. Albert.Emergence of scaling in random networks.Science, 286:509–511, 1999. pdf ()
[3] S. Boccaletti, V. Latora, Y. Moreno, M. Chavez, andD.-U. Hwang.Complex networks: Structure and dynamics.Physics Reports, 424:175–308, 2006. pdf ()
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References II
[4] J. Bollen, H. Van de Sompel, A. Hagberg,L. Bettencourt, R. Chute, M. A. Rodriguez, andB. Lyudmila.Clickstream data yields high-resolution maps ofscience.PLoS ONE, 4:e4803, 2009. pdf ()
[5] S. Bornholdt and H. G. Schuster, editors.Handbook of Graphs and Networks.Wiley-VCH, Berlin, 2003.
[6] A. Clauset, C. Moore, and M. E. J. Newman.Structural inference of hierarchies in networks, 2006.pdf ()
[7] S. N. Dorogovtsev and J. F. F. Mendes.Evolution of Networks.Oxford University Press, Oxford, UK, 2003.
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References III
[8] M. Gladwell.The Tipping Point.Little, Brown and Company, New York, 2000.
[9] A. Halevy, P. Norvig, and F. Pereira.The unreasonable effectiveness of data.IEEE Intelligent Systems, 24:8–12, 2009. pdf ()
[10] J. M. Kleinberg.Authoritative sources in a hyperlinked environment.Proc. 9th ACM-SIAM Symposium on DiscreteAlgorithms, 1998. pdf ()
[11] M. Kretzschmar and M. Morris.Measures of concurrency in networks and thespread of infectious disease.Math. Biosci., 133:165–95, 1996. pdf ()
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References IV
[12] M. Newman.Assortative mixing in networks.Phys. Rev. Lett., 89:208701, 2002. pdf ()
[13] M. E. J. Newman.The structure and function of complex networks.SIAM Review, 45(2):167–256, 2003. pdf ()
[14] I. Rodríguez-Iturbe and A. Rinaldo.Fractal River Basins: Chance and Self-Organization.
Cambridge University Press, Cambrigde, UK, 1997.
[15] S. S. Shen-Orr, R. Milo, S. Mangan, and U. Alon.Network motifs in the transcriptional regulationnetwork of Escherichia coli.Nature Genetics, 31:64–68, 2002. pdf ()
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References V
[16] F. Vega-Redondo.Complex Social Networks.Cambridge University Press, 2007.
[17] D. J. Watts.Six Degrees.Norton, New York, 2003.
[18] D. J. Watts and S. J. Strogatz.Collective dynamics of ‘small-world’ networks.Nature, 393:440–442, 1998. pdf ()
[19] E. Wigner.The unreasonable effectivenss of mathematics in thenatural sciences.Communications on Pure and Applied Mathematics,13:1–14, 1960. pdf ()