colSums()/rowSums() will be *much* faster and you can specify na.rm = TRUE.

-roger

Jonathan Baron wrote:

On 06/14/03 20:51, Jean Eid wrote:


Dear R users,
I am looking for a more efficient way to compute the sum of columns of a
matrix.
I am currently using apply(data, 2, sum) however, I am building a data set


from another one by summing the columns of some parts of the matrix.


the loop is taking too long (about 1/2 hour) for a 4462 * 202 matrix.



colSums() might be faster, but I don't know how much faster. It does not allow na.rm=T, but you don't have that, so it might help.

--
Jonathan Baron, Professor of Psychology, University of Pennsylvania
R page:               http://finzi.psych.upenn.edu/

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