[R] Help with Loops

[David Winsemius]

On May 13, 2010, at 10:49 AM, Amit Patel wrote:

> Hi
>
> I have tried many attempts but cant get the loop right, as I am not  
> a strong programmer. What I am basically trying to do is compare 2  
> spreadsheets. The problem is that one of them only contain a portion  
> of the overall data (TESTSAMP), where the other has a full  
> datasetFULLSAMP. From the complete set I would like to remove the  
> rows of data which are not in the TESTSAMP. Column 1 contains the  
> sample numbers which can be used to identify samples. Does anyone  
> have any suggestions?
>
> I have tried various things like double loops and so on, but I am  
> sure there is an easier way or function to do this.
>
> i tried this method, but Im not sure how to only keep looping until  
> a match is found. I dont understand how repeat loops work in R.
>
> for (i in 1:length(FULLSAMP[,1])) {
>
> if (FULLSAMP[i,1] != TESTSAMP[i,1]) {
> FULLSAMP <- FULLSAMP[-i,]
> }
>

Abandon the loop. Use merge.
  ... or the %in% function.
-- 

David Winsemius, MD
West Hartford, CT