Nice one - didn't think of the array at all as my brain was fixated on lists... Thanks, Murali
> Date: Fri, 24 May 2013 21:54:22 +0100 > From: ruipbarra...@sapo.pt > To: fean...@hotmail.com > CC: r-help@r-project.org > Subject: Re: [R] matrix of random variables from a matrix of means and matrix > of sd > > Hello, > > The first instruction doesn't call rnorm just once but it seems more > appropriate for your problem; > The second instruction calls rnorm just once. > > > set.seed(59187) > res1 <- replicate(10, matrix(rnorm(4, mean = a, sd = b), ncol = 2)) > > set.seed(59187) > res2 <- array(rnorm(40, mean = a, sd = b), dim = c(2, 2, 10)) > > identical(res1, res2) # TRUE > > > Hope this helps, > > Rui Barradas > > Em 24-05-2013 20:22, M M escreveu: > > folks, > > if i have a matrix of means: > > a <- matrix(1:4, 2) > > and a matrix of std deviations: > > b <- matrix(5:8, 2) > > and i want to create a matrix X of random variates such that X[i, j] is a > > draw from normal distribution with mean = a[i, j] and std dev = b[i, j], i > > think i can do this? > > X <- matrix(rnorm(4, mean = a, sd = b), ncol = 2) > > now if I want to create 10 such matrices, I could possibly do this: > > lapply(1:10, function(x) matrix(rnorm(4, mean = a, sd = b), ncol = 2)) > > is there a better way to do this with perhaps just one call to the rnorm() > > function? > > cheers, > > murali > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
