[R] pairwise comparisions

[David Winsemius]

On Sep 10, 2012, at 7:00 AM, priya wrote:

> Hi ,
> I am new to R .

How new? Is this still in a file? ... or has it been imported to an R object. If it really still is in a file,  then Bert's suggestion of first reading "Intro to R" rather than posting to R help is on point. If it is an R object, you _should_ have used dput(head(obj)) to provide an appropriate test case for solutions.

> I am facing difficulty how to make pairwise comparisions.
> For example. I have a file which looks like below
>   a b c d
> x  3 6 7 6
> y  7 8 6 5
> z  5 4 7 8
> Here I need to look for the each pairwise comparisions (ab,ac,ad,bc,bd,cd
> for each row)

Let's assume it's in a matrix of data.frame named X. To get pairwise combinations try:

CX <- combn( colnames(X), 2)

That's going to be a 2 row character matrix. Perhaps this will work but since you provide not example it will remain untested.

apply(CX, 2, function(comb), pmin(X[, comb[1]], X[, comb[2]] ) )

> For instance ,looking at first row, for x i need to look for ab values and
> take the min(3,6) >5 ,if its satistfies the count should be noted, (now
> count is 0), bc values ,min(6,7) >5 ,count for x =1 etc. Likewise all the
> comparisons are made and count is noted for x,y,z. 
> Is there any function to make pairwise comparisions in R or any easy way to
> do this?
> Any help is greatly appreciated. 
-- 

David Winsemius, MD
Alameda, CA, USA