r course 2014: lecture 6

8/10/2019 R Course 2014: Lecture 6

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Lecture 6: loops,control structures & apply fam

Simeon Lisovski

Ben Fanson


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last week dplyr

1) introduce the grammar of data manipulation

2) table verbs

3) building sentences

4) restructuring


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last week dplyr

ds %.%select(treatment, growth_rate) %.%

group_by(treatment) %.%

mutate( mean_growth = mean(growth_rate) )

ds %.%

select(treatment, growth_rate) %.%

mutate( growth_rate2 = growth_rate ^2 ) %.%

filter( treatment == 't1' )


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this week

1) loops (for, while, repeat)

2) Control structure (if else)

3) Loop families (apply, lapply, tapply)


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For Loops

for ( in ) {

}

the determines what value will take The loop is performed length(vector) times

On the nthiteration of the loop, var takes the value vector[n]

indexis a completely new variable and not directly related to anythingother variable


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Control structures

if () {

}

Sometimes, a block of code should be executed only if

condition is satisfied. In this case, the if structure can


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Control structuresYou will often need to distinguish between several cas

this case, you can extend the if structure by one or mo

clauses

if () {

} else {

}


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while() and repeat() loo

while () {

}

repeat {

if (


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apply Family


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apply Family

http://adv-r.had.co.nz/Data-st


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apply Family

A B C

ds =


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apply Family

A B C

ds =

ds %.%

mutate( D = mean(C) )


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apply Familyds %.%

mutate( D = mean(C) )A B C

ds =

D

apply(ds$C, 2, mean)

ds$D


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ds$D


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apply Familyds %.%

mutate( D = mean(C) )A B C

ds =


ds$D


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apply Family

A B C

ds =

D

1

1

2

2

tapply(ds$C, ds$D, mean)


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apply FamilyA B C

lst[[1]] =

lst =

A B C

lst[[2]] =

result


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apply FamilyA B C

lst[[1]] =

lst =

A B C

lst[[2]] =

result = c(mearesult


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Lecture 6: Hands on Sectio


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1) get Lecture6.Rfrom github

- lots of data for todays hands on section will be simulated.

Lecture 6 files

r course 2014: lecture 6

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