power.hart: Compute power for RNA-seq experiments assuming Negative Binomial distribution
Description
Use the formula of Hart et al (2013) to compute power for comparing RNA-seq expression across two groups assuming a Negative Binomial distribution. The power calculation is based on asymptotic normal approximation.
Usage
power.hart(n, alpha, log.fc, mu, sig)
Value
Vector of power estimates for the set of two-sided tests
Arguments
n
per-group sample size (scalar)
alpha
p-value threshold (scalar)
log.fc
log fold-change (vector), usual null hypothesis is log.fc=0
mu
read depth per gene (vector, same length as log.fc)
sig
coefficient of variation (CV) per gene (vector, same length as log.fc)
Details
This function is based on equation (1) of Hart et al (2013). It assumes a Negative Binomial model for RNA-seq read counts and equal sample size per group.
References
SN Hart, TM Therneau, Y Zhang, GA Poland, and J-P Kocher (2013). Calculating Sample Size Estimates for RNA Sequencing Data. Journal of Computational Biology 20: 970-978.
n.hart = 2*(qnorm(0.975)+qnorm(0.9))^2*(1/20+0.6^2)/(log(2)^2) # Equation (6) of Hart et alpower.hart(n.hart,0.05,log(2),20,0.6) # Recapitulate 90% power