[BioC] Filtering genes using a list

[mcolosim at brandeis.edu]

This probably is a general R question, but I couldn't find anything useful. I
found all sort of stuff on how to filter using functions based on the values
within the matrix, but nothing like this.

I have a list of genes in a file that I want to look at, how can I filter my
matrix of genes to match the ones in the list?

gene_list.tab with 250 genes:
probe{tab}description
affy_blah1{tab}affy gene of interest 1
affy_blah2{tab}affy gene of interest 2
..

dim(my.metric)
[1] 22625    11

mmfun <- function() # to filter
ffun <- filterfun(mmfun)
my.fmetric <- genefilter(my.metric,ffun)
dim(my.fmetric) ## This should give 250 and 11