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Old 06-16-2014, 04:46 AM   #1
Parharn
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Location: Sweden

Join Date: Jul 2013
Posts: 84
Default Zero output for sel.rn=rowSums(cnts) != 0

I get a problem when I want to try step 2 from "RNA-seq data pathway and gene-set analysis workflow" by Weijun Luo. I get zero rows with value !=0.

Code:
> p.cnts=assay(gnCnt)
> cnts=p.cnts
> dim(cnts)
[1] 7017    2
> sel.rn=rowSums(cnts) !=0
> cnts=cnts[sel.rn,]
> dim(cnts)
[1] 0 2
When I check my BAM files with IGV it looks that I have mapped reads all over the genome.
Any advise?
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Old 06-17-2014, 11:30 AM   #2
bigmw
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Default

I haven’t seen your data and exactly how you did your reads mapping and counting. But please make sure on two things:
First, you use the same version of reference genome at the TopHat step and in your TranscriptDb object.
Second, you specify the right parameters in the reads counting step. They are different for single- vs paired-end data. The workflow example is for paired-end data. Single end data are treated differently:

flag <- scanBamFlag(isNotPrimaryRead=FALSE, isProperPair=NA)
param <- ScanBamParam(flag=flag)
gnCnt <- summarizeOverlaps(exByGn, bamfls, mode="Union", ignore.strand=TRUE, single.end=TRUE, param=param)


Please check help info for details:
?scanBamFlag
?summarizeOverlaps
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Old 06-17-2014, 03:03 PM   #3
Parharn
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Location: Sweden

Join Date: Jul 2013
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Yes I got help in another thread, you are right. Thanks a lot though.
Here is the other thread just if any one wanted to know more.
https://www.biostars.org/p/103482/#103584
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