Hi, I have been trying to use the DiffBind for analyzing my ChIP-seq data; during the dba.contrast step, I came across an error that I show below.

> H3K4me3 <- dba.contrast(H3K4me3, H3K4me3$masks$V1, H3K4me3$masks$S1, "V", "S",  minMembers=2)

Error in pv.addContrast(pv, group1, group2, name1, name2) :

  Null group, can not add contrast

Could anyone tell me hwo to fix it?

Thanks,

WY

One or both of the masks (either H3K4me3$masks$V1 or H3K4me3$masks$S1) is equal to NULL. You can check the valid mask names as follows:

> names(H3K4me3$masks)

It is also worth noting that the minMembers parameter only applies when you do not specify the groups explicitly, so in this case it will be ignored.