multifactor edgeR logFC
2
0
Entering edit mode
tminning • 0
@tminning-10645
Last seen 8.4 years ago

We have a 2-factor experiment.  Factor-1 is pre vs post treatment.  Factor-2 is cured vs not-cured.  When performing edgeR I input factors as pre, post, pre, post, etc.  And lib-types were cured, cured, not-cured, not-cured, etc.  I imputed "genes" into my counts file as follows: marker pre/post up (all pre samples had read counts of 200, all post samples had read counts of  2,000); marker pre/post down (reverse of the above); marker cure up (all pre samples in cured animals had read counts of 200 and post samples in cured animals had read counts of 2,000 - for all not-cured animals both pre and post had counts of 200); marker cured down (all pre samples in cured animals had read counts of 2,000 and all post samples in cured animals had read counts 200 - all samples pre and post in not-cured animals had read counts 200).  EdgeR correctly identified my markers for cure/not-cure as significantly DE and the markers for pre/post were not significant.  BUT, the log FC for the cure/not-cure markers (marker up and marker down) were BOTH NEGATIVE.  So what am I doing wrong?  EdgeR is not finding the pattern we are looking for.  Namely, significant change between pre and post in cured but no significant change in pre vs post in not-cured.

Am I doing the factors and lib-types incorrectly?

edger • 667 views
ADD COMMENT
0
Entering edit mode

Put some code in describing what you did, a big block of text isn't very easy to read or understand.

ADD REPLY
0
Entering edit mode

Thanks for the response.  Unfortunately I'm using RNASeqGUI.  Basically a GUI for RNASeq data analysis.  So I have no code to give you.  My only imputs are the fields, factors and lib-types.  So factors are pre,post,pre,post,etc. and lib types are cured,cured,not-cured,not-cured,etc For 34 animals.  And of course I input the counts file.  Should I put something else for lib types or factors?  

ADD REPLY
0
Entering edit mode

RNASeqGUI isn't a Bioconductor package, so you'll have to ask the authors about what's happening inside their software. We can't make any statement based on what they may or may not be doing.

ADD REPLY
0
Entering edit mode
Aaron Lun ★ 28k
@alun
Last seen 10 hours ago
The city by the bay

From your description above, it seems like you're testing edgeR on some artificial data. You need to be careful when doing so, as calcNormFactors assumes that the majority of genes are not DE across samples. If this is not the case with your artificial data, then normalization will not be correct and edgeR will give the wrong DE results. To protect against this, just add a large number of non-DE genes with the same count of, e.g., 200 in all samples, before constructing the DGEList and running calcNormFactors. Note that this suggestion only applies to the construction of your artificial data set; don't manipulate counts in real data in such a manner.

ADD COMMENT
0
Entering edit mode
tminning • 0
@tminning-10645
Last seen 8.4 years ago

Okay.  Thanks again.  I suspect a lot of functionality is lost in the GUI implementation.  I wrote them a few days ago.  Still waiting.

ADD COMMENT

Login before adding your answer.

Traffic: 867 users visited in the last hour
Help About
FAQ
Access RSS
API
Stats

Use of this site constitutes acceptance of our User Agreement and Privacy Policy.

Powered by the version 2.3.6