The function rbinom might be a solution. Try following simple program : vec <- c(-1,1,-1,1,1,-1,-1,1,1)
inv <-rbinom(length(vec),1,0.5) inv <-ifelse(inv==0,-1,1) vec2 <- vec*inv #switches sign with p=0.5 In this, inv is a random binomial vector, where the probability for being 1 is 0.5 in all positions. Changing the values of 0 in this vector to -1, gives you a vector you can multiply with the original one to change the sign with a probability of 0.5 for all positions Kind regards Joris On Tue, Nov 18, 2008 at 6:11 PM, Salas, Andria Kay <[EMAIL PROTECTED]> wrote: > To clear up a question regarding my earlier posting regarding random changes > in a vector: > > Say you have a vector (1, -1, -1, 1, 1, -1). I want each value in the vector > to have a probability that it will change signs when this vector is > regenerated. For example, probability = 50%. When the vector is > regenerated, the first value in the vector (1) has a 50% chance of switching > to -1. If I regenerated this vector 10 times, 5 of the times it would switch > to -1. Similarly, I need each value in the vector to have this same > probability of switching signs when the vector is regenerated, and each > value's chances of doing so is independent of the other values. So the > second value (-1) also has a 50% chance of switching to 1, and whether or not > it does so is independent of if the first value changes from 1 to -1 (also a > 50% probability). > > I hope this clears up the confusion, and I would appreciate any help anyone > can provide! > ______________________________________________ > 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. > ______________________________________________ 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.
