[R] Using functions/loops for repetitive commands

[Gerrit Eichner]

Hello, Derek,

first of all, be very aware of what David Winsemius said; you are about to 
enter the area of "unprincipled data-mining" (as he called it) with its 
trap -- one of many -- of multiple testing. So, *if* you know what the 
consequences and possible remedies are, a purely R-syntactic "solution" to 
your problem might be the (again not fully tested) hack below.


> If so how can I change my code to automate the chisq.test in the same 
> way I did for the wilcox.test?

Try

lapply( <your_data_frame>[<selection_of_relevant_components>],
         function( y)
          chisq.test( y, <your_data_frame>$<group_name>)
       )

or even shorter:

lapply( <your_data_frame>[<selection_of_relevant_components>],
         chisq.test, <your_data_frame>$<group_name>
       )


However, in the resulting output you will not be seeing the names of the 
variables that went into the first argument of chisq.test(). This is a 
little bit more complicated to resolve:

lapply( names( <your_data_frame>[<selection_of_relevant_components>]),
         function( y)
          eval( substitute( chisq.test( <your_data_frame>$y0,
                                        <your_data_frame>$tension),
                            list( y0 = y) ) )
        )



Still another possibility is to use xtabs() (with its summary-method) 
which has a formula argument.


  Hoping that you know what to do with the results  --  Gerrit

---------------------------------------------------------------------
Dr. Gerrit Eichner                   Mathematical Institute, Room 212
gerrit.eichner at math.uni-giessen.de   Justus-Liebig-University Giessen
Tel: +49-(0)641-99-32104          Arndtstr. 2, 35392 Giessen, Germany
Fax: +49-(0)641-99-32109        http://www.uni-giessen.de/cms/eichner