[R] Evaluating matrices without using loops

vincent.deluard vincent.deluard at trimtabs.com
Sun May 9 06:13:49 CEST 2010

Hi R users,

I am trying to set the values of elements of one matrix based on the values
of elements of another matrix.

Say I have 2 matrices, y and z.

y = matrix(rnorm(35), ncol=5)
z = matrix(rep(0,35), ncol=5)

I want z[i,j] to take a value  of y[i,j] when y[i,j] is greater than 0, and
zero otherwise.

I was able to do it using the following loop:

for(i in 1:7) 


	for(j in 1:5) 

		if(y[i,j]>0) {
			} else {

but since my dataset is very large, looping often crashes. Is there a more
elegant way I can achieve the same result?

Many thanks!!!
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