Easier than Excel: Social Network Analysis of

DocGraph with GephiJanos G. Hajagos

Stony Brook School of Medicine

Fred Trotterfredtrotter.com

DocGraph Based on FOIA request to CMS by Fred Trotter

Pre-released at Strata RX 2012

Medicare providers (more than doctors)

CY 2011 dates of service

Share 11 or more patients in a 30 day forward window

Initial access restricted to MedStartr funders

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DocGraph by the numbers Directed graph

Average total degree 52.8

940,492 providers (graph nodes/vertices)

49,685,810 shared edges

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Geographic visualization

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http://isurfsoftware.com/blog/2012/12/13/visualizing-geographic-connections-between-us-doctors/

DocGraph data

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NPPES National Plan and Provider Enumeration System

Source of NPI (National Provider Identifier)

No cost download Information is entered and updated by provider

- Data quality is good to poor CSV file with 314 columns A custom MySQL load script is used to normalize the database

Bloom.api open source project to make data easier to access

- http://www.bloomapi.com/

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Tabular data

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Things we can do with tabular data

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Graph dataRelation between authors and MeSH terms from PubMed

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http://dx.doi.org/10.6084/m9.figshare.94595

Graph types Undirected graph

- Facebook friendships

Directed graph

- Twitter: follow and be followed

Bipartite graph

Multipartite

- RDF graph model

- Property graph model

Allow parallel edges

- RDF graph Model

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Components of a network/graph

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Graphs in healthcare Prescriber and patient (bipartite)

- NCPDP data with NPI

Referral data sets

Shared patients

- DocGraph

Social networks

- Tweeting about a disease

Limited by imagination

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Generating GraphML XML based file format for graphs

Readable by a large number of tools

- Gephi

- Mathematica

- igraph (R)

NetworkX a Python library for graphs which can export to GraphML

GraphML is not a file format for really large graphs

GraphML is not readable by d3.js

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GraphML can be loaded into Mathematica

Gephi

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Gephi Java based open source tool

Focused on interactivity

- Fast graphics

- Multi-threaded

- Visual updates

Strong graph analytics

Graphs stored in memory

- Upper limit is about 100,000 nodes

Netbeans plugin architecture

- Integration with Neo4J

- Additional layout algorithms

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Downloading Gephi

http://gephi.org/users/download/

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Downloading sample files

https://dl.dropboxusercontent.com/u/21690634/DocGraph/docgraph_tutorial_examples.zip

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Subsets are generated using a Python script

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python extract_providers_to_graphml.py "npi='1750499653'" sterrence Leaf-edgesOpening connection referralConfigurationSelection criteria for subset graph: npi='1750499653'Referral table _name: referral.referral2011NPI detail table name: referral.npi_summary_primary_taxonomyNodes will be labeled by: provider_nameLeaf-to-leaf edges will be exported? False…Imported 1 nodes…Imported 986 nodes…Imported 1724 edgesEdge types imported{'core-to-leaf': 866, 'leaf-to-core': 856: None : 2}Leaf-to-leaf edges were not selected for exportWriting GraphML file

Generating a subset: some concepts

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Core nodes

Adding leaf nodes

Connecting core nodes

Connecting to leaf nodes

Connecting leaf nodes

Sample files jamestown_core_provider_graph.graphml

- Providers selected with practice addresses in Jamestown, NY

- Small city in far western New York (approximately 30,000 residents)

- 179 nodes with 5,560 edges

jamestown_core_and_leaf_provider_graph.graphml

- Includes providers above and those who are linked to them

- 1,322 nodes with 12,457 edges

albany_core_provider_graph.graphml

- Providers selected with practice addresses in Albany, NY

- A small city in New York (approximately 100,000 residents)

- 1,368 nodes with 44,711 edges

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Sample files (continued) bronx_core_provider_graph.graphml

- Providers selected with practice addresses in Bronx, NY

- Urban community (1.4 million residents)

- 3,268 nodes and 53,828 edges

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Opening a graph file

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Import report

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Force directed layout of the graph

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Results of the layout

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ForceAtlas 2 works well for larger graphs

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Navigating the graph Best experience with a three button mouse with a scroll wheel

- Right click and hold to pan

- Scroll wheel to zoom in and out

- Left click to select

- Right click for context menus

MacBook users

- command key and click and hold down on trackpad to pan

- Two fingers to zoom on trackpad

- Click on trackpad to select

- Control click for context menus

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Coloring the graph (partitioning)

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Coloring the graph (partitioning)

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Varying node size based on importance Step 1: Need to select a measure for node importance

- Degree

- PageRank

- Eigenvector centrality

Step 2: Run the measure against the graph

Step 3: Ranking tab and “Size/Weight”

Step 4: Set size range

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Graph measures Degree

- In-degree

- Out-degree

Graph structure measures

- Clustering (global and local)

- Network diameter

Centrality Measures

- Eigenvector centrality

- PageRank (Google search)

Community measures

And more . . . . .

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Interactively viewing node attributes

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Click the “T” icon on the bottom to turn on node labeling

Data Laboratory

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Selecting visible fields

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Viewing edge attributes

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Saving your graph Save your graph in .gephi format

- xml based format

- preserves layout, size, and color

Save in GraphML format for use with outside programs

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Filtering nodes by attributes

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Hints for filtering nodes Drag field filter “is_physician” from the top pane to the lower pane

Set the value to filter on

- Value should equal 1

- 1 is equivalent to true

Click “Filter” to apply

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Producing a final graph

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We need to rescale the edge weights in the graph

Producing a final graph after scaling

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Bronx core provider graph

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Challenge questions Which institution is the most “important” provider for the Bronx?

- Hint: try a centrality measure

Can you determine if geography plays a role in patient sharing in the Bronx?

- Which parameter could be used to partition the graph?

Can you filter the graph to show only radiologists?

Which radiologist has the highest “authority” in the graph?

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Other tools for graph analysis NetworkX

- Python

- Lots of algorithms

igraph

- R and Python

Gremlin – graph traversal and manipulation

- Groovy shell

- Gremlin interface is implemented for Neo4J

And more . . .

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Scaling the analysis to the entire DocGraph Most healthcare graphs will be big (millions of nodes)

What we learn at the local level can be applied at the global level

- Importance of geography

- Supernodes (radiologist, ER docs, pathologist, transportation, …)

Many graph measures don’t scale well

- Maximal cliques

Currently exploring how to use Faunus to scale the analysiswith Hadoop

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Linkshttp://strata.oreilly.com/2012/11/docgraph-open-social-doctor-data.html (information)

https://github.com/jhajagos/DocGraph (code)

http://notonlydev.com/docgraph-data/ (open source $1 covers bandwidth fees)

https://groups.google.com/forum/#!forum/docgraph (mailing list)

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Questions

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Try to publish your own healthcare dataset as a graph!