Count the number of non-zero elements of each column

Question

Very new to R and I have a .rda file that contains a matrix of gene IDs and counts for each ID in 96 columns. It looks like this:

Answer 1

Another method using plyr's numcolwise:

library(plyr)

dat <- data.frame(a = sample(1:25, 25),
                  b = rep(0, 25),
                  c = sample(1:25, 25))
nonzero <- function(x) sum(x != 0)
numcolwise(nonzero)(dat)
   a b  c
1 25 0 25