more efficient sum of matrix columns

From: Jean Eid <jeaneid at chass.utoronto.ca>
Date: zon jun 15, 2003  02:51:29 Europe/Amsterdam
To: r-help at stat.math.ethz.ch
Subject: [R] more efficient sum of matrix columns


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.
thanks,
Jean Eid