Hi
I'm trying to set up a simulation problem without resorting to (m)any loops. I want to set entries in a data frame of zeros ('starts' in the code below) to 1 at certain points and the points have been randomly generated and stored in a separate data.frame ('sl'), which has the same number of columns.

An example of the procedure is as follows:
ml <- data.frame(matrix(sample(1:50,80, replace=TRUE),20,4))
mm <- apply(ml, 2, cumsum)
starts<- data.frame(matrix(0,600,4))

I can achieve the result I want with a loop:
for (i in 1:4){
lstarts[,i][mm[,i]] <-1
}

But as I want to use a large number of columns I would like to do away with the loop

Can anyone suggest how this might be done?

Thanks in advance

Brett Robinson

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