[R] columnwise nnzero for dgCMatrix

[C6H5NO2]

Hi R users,

I want to know whether there is a fast method to compute the nonzeroes for
each column of dgCMatrix.

For summation or average I can use colSums or colMeans. To count the
non-zeroes I write a function

colCounts <- function(Mat) {
    M1 <- apply(Mat, MARGIN=2, FUN=nnzero)
}

But it seems this is quite slow because the apply function would transform a
dgCMatrix to a matrix.

So I come here to ask if there is anybody know some fast method.

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