[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) {
z[i,j]=y[i,j]
} else {
z[i,j]=0}}
}
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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