[R] Help on selecting genes showing highest variance

[GIS Visitor 33]

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