gene FPKM from eXpress

[Golsheed]

Hello,

I want to calculate gene-level FPKM values from eXpress data. From eXpress output, I have FPKM values for each isoform of a gene.

(1) Can I just sum the FPKM values for all isoforms of a given gene to get that gene's FPKM value? If not, what's the correct way to do that?

(2) If the above-mentioned method is correct, can someone please briefly
explain why it works?

Any help is much appreciated.

Thanks,
Golsheed

[shunyip]

No, it doesn't work. Please look at FPKM's formula.

Instead, you should sum up the raw counts of your gene and then use it to calculate its FPKM.