Is there any way to "force" 0 * NA to be 0 instead of NA? For example, suppose I have a vector with some valid values, while other values are NA. If I matrix-pre-multiply this by a weight row vector, whose weights that correspond to the NAs are zero, the outcome will still be NA: x <- c(1, NA, 1) wt <- c(2, 0, 1) wt %*% x # NA Alberto Monteiro