[BioC] to extract just some columns of an exprsSet

[Florence Combes]

Dear all,

I have a programming problem with R, but in connection with arrays:
My goal is to extract just some columns (for which I have the label of 
each) of an object of exprsSet type: the resulting object of the expresso() 
command from the affy package.

To be precise, let's say that I have 12 arrays, so my exprsSet object is a 
matrix of some thousands  of lines by 12 columns.

My problem is that I don't have the rank of the columns I want to extract, 
but just the labels.
Let's say I have a matrix of 12 colums labelled "sample1" to sample12". I 
want to extract the columns labelled "sample1", sample4" and sample6", 
which are non contiguous on my exprsSet matrix, in order to create a new 
matrix with these columns only.

I do not know how to obtain the indices (coordonates is maybe better?) of 
these 3 columns.
I think that when I will have these indices I will the be possible to use 
the subset() command ?

Does anyone could help me with this, because it seems I won't be able to do 
....

Thanks a lot for your help,

Florence.