[R] conditional function definition?

Spencer Graves spencer.graves at pdf.com
Sat Sep 20 17:12:52 CEST 2003

Have you considered: 

 > exists("slice.index")
[1] TRUE

       In other circumstances, I've tested various components of 

hope this helps. 
spencer graves

(Ted Harding) wrote:

>Hi Folks,
>What is the best way to avoid a function being read in
>anew (and masking an exiting function) when a definition
>of it has already been established in R?
>Reason: Fernando Tusell and I are working up Schafer's 'CAT'
>for R (basically done now, just needs some cosmetic tidying up).
>This uses a function 'slice.index', present in S but not in
>the versions of R we were working with at the time. So we put
>in a definition (copied from R-help ... ).
>However, it seems that slice.index is now in "base" in latest
>versions of R. So it would seem a bit silly to read it in anew.
>Nevertheless, probably we should keep it in for the sake of people
>still using older versions of R who would not have it.
>So what's the best method to do
>if( some test for function slice.index absent ) {
>  slice.index<-function(....){....}
>E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
>Fax-to-email: +44 (0)870 167 1972
>Date: 20-Sep-03                                       Time: 15:07:59
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