[R] Generating a new matrix using rbinom and a matrix of probabilities.

[Patrick Burns]

I think the following does what you want:

probMatrix <- matrix(runif(5 * 5), 5, 5)
binomialMatrix <- matrix(rbinom(5 * 5, 1, probMatrix), 5, 5)


Patrick Burns
patrick at burns-stat.com
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http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")

Economics Guy wrote:

>I am having a little trouble getting R to do something without writing
>a couple of very awkward loops.
>
>I have a matrix of probabilities and I want to generate a new matrix
>of ones and zeros where each element in the new matrix is the result
>of a draw from a binomial distribution where the probability of
>getting a 1 is the corresponding element in the matrix of
>probabilities.
>
>Example Code:
>--------------------------------------------
>
>## First I generate the matrix of probabilities for example purposes.
>
>probMatrix <- matrix(NA,5,5){
>
>for (i in 1:5)
>
>probVectorI <- runif(5,0,1)
>
>probMatrix[i,] <- probVectorI
>
>}
>
># Now I want to take each element in probMatrix and use it as the
>probability parameter in rbinom draw and generate a new matrix.
>Something like this:
>
>binomialMatrix <- rbinom(1,1,probMatrix)
>
># But that does not work. I know I can run a loop across each vector
>of the matrix, but this seems like an bad way to do this.
>
>---------------------------End Code--------------------------------
>
>So any help would be appreciated.
>
>Thanks,
>
>EG
>
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