[BioC] how to design matrix by edgeR

[wang peter]

Dear Gordon,
thank you very much. i want to find genes are DE at
each time vs 0h, adjusting for control differences?


i know i should do such work:
treatment=factor(c(rep('treated',24),rep('control',11)))
time=factor( c('oh','oh','oh','6h','6h','6h','6h','12h',
'12h','12h','12h','18h','18h','18h','18h','24h','24h','24h','36h','36h','36h','48h','48h','48h','oh',
         'oh','oh','6h','12h','18h','24h','36h','48h'))

but i donot understand how to design the matrix?
design <- model.matrix(~treatment+tissue)?
design <- model.matrix(~treatment*tissue)

do you have some reference to tell me how to use the model.matrix function

thank you very much


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shan gao
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