[R] How to run Shapiro-Wilk test for each grouped variable?

David Winsemius dwinsemius at comcast.net
Fri Apr 9 15:17:25 CEST 2010

On Apr 9, 2010, at 8:16 AM, Iurie Malai wrote:

> I want to run Shapiro-Wilk test for each variable in my dataset, each
> grouped by variable groupFactor.
> I have these working commands:
>> data.n<-names(data) # put names into a vector called data.n
>> by(eval(parse(text=(paste("data",data.n[3],sep="$")))), data 
>> $factor, shapiro.test) #run shapiro.test
> but I must to change the variable number manualy. How to automate  
> this?
> I tried this:
>> for (r in 3:18) {
>> by(eval(parse(text=(paste("data",data.n[3],sep="$")))), data 
>> $groupFactor, shapiro.test)
>> }

Not able to test since you have provided code that works with data  
that is not available. Inside for loops one needs either to make an  
assignment or print the results. Had the data been available I would  
have wrapped print() around the full by expression to see if my  
hypothesis could be tested.

> but not working and no errors. Why?
> Please help.
> -- 
> Regards,
> Iurie Malai, Senior Lecturer
> Department of Psychology
> Faculty of Psychology and Special Education
> Ion Creanga Moldova Pedagogical State University - www.upsm.md
> http://en.wikipedia.org/wiki/Ion_Creang%C4%83_Pedagogical_State_University
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT

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