[R] Phi coefficient matrix (package psych)
William Revelle
lists at revelle.net
Mon Apr 27 05:05:37 CEST 2015
>
> Kumar and Jim,
> The phi coefficient is identical to the Pearson coefficient in the case of a 2 x 2 data set.
>
> As it says in the help file for phi:
>
> "Since the phi coefficient is just a Pearson correlation applied to dichotomous data, to find a matrix of phis from a data set involves just finding the correlations using cor or lowerCor or corr.test.”
>
> So, you can do a cor(df) and you do not need the phi(df)
>
> If you want the tetrachoric (which estimates what a Pearson would be if you had not artificially dichotomized the data) try tetrachoric(df)
>
> Bill
>
>
>
>
>> On Apr 21, 2015, at 3:34 PM, Kumar Mainali <kpmainali at gmail.com> wrote:
>>
>> I want to calculate phi coefficient for every pair of the columns. Is there
>> a way to generate a matrix like a correlation matrix? I know cor function
>> in the case below gives same answer as phi coefficient.
>>
>> x <- sample(c(0,1), 10, replace=TRUE)
>> y <- sample(c(0,1), 10, replace=TRUE)
>> z <- sample(c(0,1), 10, replace=TRUE)
>> df <- data.frame(x,y,z)
>> cor(df)
>> library(psych)
>> phi(df)
>>
>> Thank you,
>> Kumar Mainali
>> Postdoctoral Associate
>> Department of Biology
>> University of Maryland
>> ᐧ
>>
>> [[alternative HTML version deleted]]
>>
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>
> William Revelle http://personality-project.org/revelle.html
> Professor http://personality-project.org
> Department of Psychology http://www.wcas.northwestern.edu/psych/
> Northwestern University http://www.northwestern.edu/
> Use R for psychology http://personality-project.org/r
> It is 3 minutes to midnight http://www.thebulletin.org
>
>
>
>
>
>
William Revelle http://personality-project.org/revelle.html
Professor http://personality-project.org
Department of Psychology http://www.wcas.northwestern.edu/psych/
Northwestern University http://www.northwestern.edu/
Use R for psychology http://personality-project.org/r
It is 3 minutes to midnight http://www.thebulletin.org
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