count/rpkm/tpm之间转换代码

标准化方法原理：https://hbctraining.github.io/DGE_workshop/lessons/02_DGE_count_normalization.html
参考链接：https://zhuanlan.zhihu.com/p/150300801

countToTpm <- function(counts, effLen)
{
    rate <- log(counts) - log(effLen)
    denom <- log(sum(exp(rate)))
    exp(rate - denom + log(1e6))
}
 
countToFpkm <- function(counts, effLen)
{
    N <- sum(counts)
    exp( log(counts) + log(1e9) - log(effLen) - log(N) )
}
 
fpkmToTpm <- function(fpkm)
{
    exp(log(fpkm) - log(sum(fpkm)) + log(1e6))
}