Dear all,
I am pretty sure that this has been discussed before. Unfortunately, I
can not find anything in the archives -- probably because I am
"RSiteSearching" for the wrong terms. If I remember correctly, I think I
even asked this question a few years ago. But I cannot even find this.
The basic problem is that a result depends on a previous result. This is
easy with a loop--but how can I do this without a loop?
Lets give an example:
initial.matrix <- rbind(rep(1,4), matrix(0,ncol=4,nrow=5))
the.other.matrix <- matrix(runif(20), ncol=4, nrow=5)
the initial matrix should be filled according to the following
(pseudo-code) rule:
if (row==1) initial.matrix[1,] <- 1
if (row>1) initial.matrix[x,] <- initial.matrix[x-1,] *
the.other.matrix[x-1,]
as I said this is easy to do with a loop:
for (i in 2:(nrow(initial.matrix))) {
initial.matrix[i,] <- initial.matrix[i-1,]*the.other.matrix[i-1,]
}
initial.matrix
But how can I do this without a loop?
Thank you already in advance!
Roland
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