Generate the numbers, test for zero and then set negatives to zero: > set.seed(1) > x <- rnorm(100,5,3) > sum(x<0) [1] 3 > x[x<0] <- 0 > sum(x<0) [1] 0 >
On Mon, Nov 16, 2009 at 7:43 AM, Rafael Moral <rafa_moral2...@yahoo.com.br> wrote: > Dear useRs, > > I wrote a function that simulates a stochastic model in discrete time. > The problem is that the stochastic parameters should not be negative and > sometimes they happen to be. > How can I conditionate it to when it draws a negative number, it transforms > into zero in that time step? > > Here is the function: > > stochastic_prost <- function(Fmean, Fsd, Smean, Ssd, f, s, n, time, > out=FALSE, plot=TRUE) { > nt <- rep(0, time) > nt[1] <- n > for(n in 2:time) { > nt[n] <- 0.5*rnorm(1, Fmean, Fsd)*rnorm(1, Smean, > Ssd)*exp(1)^(-(f+s)*nt[n-1])*nt[n-1]} > if(out==TRUE) {print(data.frame(nt))} > if(plot==TRUE) {plot(1:time, nt, type='l', main='Simulation', > ylab='Population', xlab='Generations')} > } > > The 2 rnorm()'s should not be negative; when negative they should turn into > zero. > > Thanks in advance, > Rafael > > > > ____________________________________________________________________________________ > [[elided Yahoo spam]] > > [[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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ 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.