Hi everyone, I'm not sure what should be done about it, but I've been surprised with the following behavior with normalizeBetweenArrays: (dat is an MAList here) > dat$A[1,1] [1] 8.796361 > dat <- normalizeBetweenArrays(dat) > dat$A[1,1] [1] Inf This is due to the fact that I've got almost 400 arrays here. The normalizeMedians(x) (which is called by normalizeBetweenArrays) has the following behavior: a.med <- apply(x, 2, median, na.rm = TRUE) a.med <- a.med/(prod(a.med))^(1/narrays) multiplying 400 relatively small numbers can easily reach R's limit as far as doubles are concerned. > 6^400 [1] Inf Wouldn't it be better to be working in log space instead? Francois > sessionInfo() R version 2.1.0, 2005-04-18, x86_64-unknown-linux-gnu attached base packages: [1] "methods" "stats" "graphics" "grDevices" "utils" "datasets" [7] "base" other attached packages: limma "1.9.6"