If you already have the column sums vector supply it, otherwise leave it NULL.
std
A boolean variable specyfying whether you want the variances (FALSE) or the standard deviations (TRUE) of each column.
Value
A vector with the colum variances or standard deviations.
Details
We found this in stackoverflow and was created by David Arenburg.
We then modified the function to match the sums type formula of the variance, which is faster.