Can edgeR do trend anaysis?

[shirley47162928]

In edgeR we have found DE genes beween two categorical groups .
Now the group has 3 levels, we want to see if there is a trend for these DE analysis. How to do it?

[Gordon Smyth]

Just put the numerical levels into a column of the design matrix:

x <- numerical values
design <- model.matrix(~x)

Then do DE analysis for this coefficient.