Is it appropriate to apply quantile normalization on RNA-Seq before computing the Pearson correlation?
Is it appropriate to apply quantile normalization on RNA-Seq before computing the Pearson correlation? Specifically, RNA-Seq data displays a dense tail distribution, and Person's correlation (cor function in R) assumes a normal distribution. I tried this in R using the normalize.quantiles function discussed in the lecture, and my results make a lot of sense, but I want to make sure that this is an appropriate transformation before accepting these results.
Thank you for your help!
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Of course you will get normal distributions out of
normalize.quantilesbut I wouldn't count on it. The main problem is the low counts, you will get random effects amplified. I would try spearman's correlation instead but make sure you normalize for library size first.Yes. My pipeline is rawcounts-->DESeq2-->normalized.quantiles Or do you suggest normalizing the rawcounts using a different method? Is there an R function to do the library normalization?
DESeq2 normalization is great. Maybe try spearman's on the normalized count table. Make sure the
rdistribution looks good. You can use thenormalize.quantilesbut just make sure you're not getting artifacts from 0 counts.Yes. I am removing rowMeans<10.