Hi Gordon,

Thanks for the info. My apologies for being unclear, I meant the function
estimateCommonDisp (and estimateTagwiseDisp) in the package edgeR. I guess
the attachment didn't go through, I've pasted it below

-Jacob

R script:
library(edgeR)


groups <- factor(c("A", "A", "B", "B", "C", "C"))
rows <- 10
cols <- 6
counts <- matrix( rnorm(rows*cols,mean=100,sd=20), nrow=rows, ncol=cols)
counts <- round(counts)

#Everything runs smoothly
y <- DGEList(counts=counts,group=groups)
y <- calcNormFactors(y)
y <- estimateCommonDisp(y)
print(y$common.disp)
#[1] 0.0310142

#Take out samples from group "B", estimating the dispersion fails
sel_cols <- c(1,2,5,6)
counts <- counts[,sel_cols]
groups <- groups[sel_cols]
y <- DGEList(counts=counts,group=groups)
y <- calcNormFactors(y)
y <- estimateCommonDisp(y)
print(y$common.disp)
#[1] 99.99477
print(warnings())


On Wed, Jun 4, 2014 at 8:21 PM, Gordon K Smyth <smyth@wehi.edu.au> wrote:

> Dear Jacob,
>
> There is no function called edgeR.calculateCommonDispersion in the edgeR
> package.
>
> There also wasn't any attachment with your posting.
>
> If you subset a DGEList in such a way that a group is removed entirely,
> you can prevent any problems by resetting the levels of the group factor:
>
>  dge$samples$group <- factor(dge$samples$group)
>
> Best wishes
> Gordon
>
>
>
> ----------- original message ------------
> Jacob Silterra jacob at broadinstitute.org
> Wed Jun 4 19:45:50 CEST 2014
>
>
> Hello all,
>
> I've encountered an issue with edgeR when it calculates dispersion, and
> there aren't any samples for a given group. I believe it happens with both
> tagwise and common dispersion; same idea. Basically splitIntoGroups will
> return an empty matrix for that group, which messes up the dispersion
> calculation. I think it would be better to ignore groups that have no data
> associated with them. Example attached. This might seem unnecessary, but I
> have a situation where I read in a matrix with samples of different classes
> and then remove some groups entirely
>
> Thanks,
> --
> Jacob Silterra
> Associate Computational Biologist
> Broad Institute
>
> ______________________________________________________________________
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