R help - Jul 2011 - subset with aggregate key

Hello:

I am working on trying to subset a data.frame using a vector of headings 
as a single 'key'. I have things to the point where I can get the unique
sets of keys but I'm stuck on how to use these in a subset call.

So far, I've got something similar to:


    cols <- c('V1','V2')
    keys <- unique (subset (df, select = cols))

This gives me something like:

    > keys
      V1 V2
    1  1  2
    2  1  3
    3  2  1
    4  4  1

What I'd like is to be able, for each row of keys, to do something 
similar to:

    subset (df, c('V1',V2') == keys[1,])

Which is obviously invalid.

Any suggestions on what is the best way to get the subset from this 
aggregate key? This example has only two columns selected but I need to 
support a variable number of columns used as the 'key'

Thanks,

Jesse