[BioC] Using eBayes to find P values for individual contrasts
Jason Shoemaker
jshoe at ims.u-tokyo.ac.jp
Tue Nov 16 09:28:52 CET 2010
Dear all,
I have searched the archives but not found any
advice on this issue. I am using the LIMMA package
to determine differentially expressed genes. I
have been using eBayes plus topTable to find the
most differentially expressed genes, but now I
want to determine the adjusted p values specific
for each contrast. Should I simply do as follows
(following the example from
http://matticklab.com/index.php?title=Single_channel_analysis_of_Agilent_microarray_data_with_Limma):
contrast.matrix <-
makeContrasts("Treatment1-Treatment2",
"Treatment1-Treatment3", "Treatment2-Treatment1",
levels=design);
fit2 <- contrasts.fit(fit, contrast.matrix)
fit2 <- eBayes(fit2)
P.values<-p.adjust(fit2$p.values,methods="fdr");
in doing so- can I make fair comparisons between p
values for each contrast? Or more precisely, if a
get a p value of 0.01 for "Treatment1-Treatment2"
and large value (P>0.1) for the remaining 2
contrasts, is that gene significant only for
"Treatment1-Treatment2"?
Thank you!
Jason
More information about the Bioconductor
mailing list