[BioC] subsetting an eset object with a defined list

[Celine Carret]

Hi,
I'm stuck remembering the way of subsetting an eset object (19 affy 
arrays) to accomodate only a defined list of genes that I'm interested in.
I read.table(list) into R, transformed it as.matrix and use the functions:
exprs(eset)[list] or
exprs(eset)[as.character(list)]

those functions recognize that I have 904 genes in that list, but gives 
me 904 NA
What I would like to obtain is my 904 genes with the values for the 19 
arrays, in order to assess the DE only on this subgroup as the other 
genes are not supposed to be expressed at this stage of the cultures I'm 
looking at.
Could someone please point me in the right direction?
Thank you very much
Celine



sessionInfo()
Version 2.3.0 (2006-04-24)
ia64-unknown-linux-gnu

attached base packages:
[1] "splines"   "tools"     "methods"   "stats"     "graphics"  "grDevices"
[7] "utils"     "datasets"  "base"    

other attached packages:
affycoretools       GOstats      Category      hgu95av2          KEGG
      "1.4.0"       "1.6.0"       "1.4.1"      "1.12.0"      "1.12.0"
     multtest    genefilter      survival        xtable          RBGL
     "1.10.2"      "1.10.1"        "2.24"       "1.3-2"       "1.8.1"
     annotate            GO         graph         Ruuid         limma
     "1.10.0"      "1.12.0"      "1.10.6"       "1.9.2"      "2.7.10"
         affy        affyio       Biobase
     "1.10.0"      "0.99.3"      "1.10.1"


-- 
----------------------------------------------------
Celine Carret PhD
Pathogen Microarrays group
The Wellcome Trust Sanger Institute
Hinxton, Cambridge CB10 1SA, UK.
tel. +44 (0)1223 494 940
fax. +44 (0)1223 494 919
email: ckc at sanger.ac.uk
http://www.sanger.ac.uk/PostGenomics/PathogenArrays/