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Getting Probe Ids For Expression Matrix Before Summarisation (In R If Possible)

Hi guys

Anyone know how to get the probe set ids for the expression matrix row names BEFORE summarisation (so like 140292811, 140292812 etc.). When I load the cel files into R, the original unnormalised expression matrix has row names from 1:number of probes:

library(oligo) 
geneCELs <- list.celfiles(path, full.names=TRUE)
affyGeneFS <- read.celfiles(geneCELs)
genePS <- rma(affyGeneFS, target="probeset") 
featureData(genePS) <- getNetAffx(genePS, "probeset")

so I can do exprs(genePS) and get the probesets, however I want the original probes, before they are "summarised" to the probe-set level. So something like: exprs(affyGeneFS). However this gives sequential row names as I said before.

Does anyone have any ideas? Perhaps the affy package is better suited?

J

r microarray

3 answers

Hi Jimbo,

If you have an Affymetrix chip which measures gene expression, I would indeed use the affy package instead of the oligo package. This should solve your problem with the missing probe set names.

Christof

netaffy at affymetrix.com has descriptions of each of Affymetrix chip layouts which are compatible with bioconductor. You will need the one for the genechip you are using. Bill

For some platforms, such as hugene 2.0 st, affy can not deal with the preprocessing part, only oligo or xps can deal with it.

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