Question: Strange Mean-Variance plot after Voom Normalization (RNAseq)

0

grayapply2009 •

**210**wrote:I normalized my raw counts using Voom (limma package) and got a strange Mean-Variance plot https://ibb.co/C2RZXGk . It doesn't look right.

Any suggestions about why and how to deal with it?

ADD COMMENT
• link
•
modified 5 weeks ago
by
Biostar ♦♦

**20**• written 5 weeks ago by grayapply2009 •**210**
That does indeed look very stange! How did you quantify your samples? How many samples do you have? Did you do any filtering before using voom - if so how?

3.4kThanks for your reply. Here is what I did: 1. Quantification: fastq -> count table (Star + featurecounts, mm10, N = 30) 2. Remove lowly expressed genes: genes showing less than or equal to 1 count in 30% samples were removed 3. Voom (TMM) normalization

The following plot is the voom normalization without removing any genes (https://ibb.co/6N8by9B).

210Probably this isn't the problem, but the variance is (standard deviation)^2 while you are plotting sqrt(standard deviation).

2.6k