Hi, just as the title.
When using microarray, the intensity should be log transformed, that is partly because the intensity values are relative numbers. But in RNA-Seq, why must RPKM be log transformed?
I also notice that the differential analysis results are largely different with/without log transform. why? anyone tell me? thank you.
Who told you this? Log transformed expression are easier to detect DEG with low expression level. However, I never heard it's a must to log transformed them.
I just saw this transformation on many papers resolved with RPKM and microarray expression data. It seems to be a usual convention.
Btw, I guess that low expression levels are not believable, so I always to filter with some threshold value.