search for: leukemiadata

Hi I have a problem for which I would like to know a solution. I have a gene expression data and I would like to choose only lets say top 200 genes that had the highest expression variance across patients. How do i do this in R? I tried x=apply(leukemiadata,1,var) x1=x[order(-1*x)] but the problem here is x and x1 are numeric data , If I choose the first 200 after sorting in descending, so I do not know how to choose the associated samples with just the numeric values. Kindly help! Regards Ap