I have calculated a rate ratio for the rate of genetic mutations in a patient group vs. control group. The rate for each group is calculated as (mutation rate)/(number of samples * number of callable base pairs) and the significance is calculated for ratio>1. I now am interested in calculating the power I have to detect a certain difference in rate (i.e. how much greater than 1 the rate ratio is) based on the number of samples and number of callable bases in each group.

Does anyone know of a straightforward way to do this? I haven't found an answer from my searching the internet, and the R package I used to do the rate ratio test doesn't give power. Thanks!!