You probably want to generate data from a Dirichlet distribution. There are some functions in packages that will do this and give you more background, or you can just generate 4 numbers from an exponential (or gamma) distribution and divide them by their sum.
-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Alexander Engelhardt > Sent: Monday, October 10, 2011 10:11 AM > To: r-help > Subject: [R] How to draw 4 random weights that sum up to 1? > > Hey list, > > This might be a more general question and not that R-specific. Sorry > for > that. > > I'm trying to draw a random vector of 4 numbers that sum up to 1. > My first approach was something like > > a <- runif(1) > b <- runif(1, max=1-a) > c <- runif(1, max=1-a-b) > d <- 1-a-b-c > > but this kind of distorts the results, right? > Would the following be a good approach? > > w <- sample(1:100, 4, replace=TRUE) > w <- w/sum(w) > > I'd prefer a general algorithm-kind of answer to a specific R function > (if there is any). Although a function name would help too, if I can > sourcedive. > > Thanks in advance, > Alex > > ______________________________________________ > 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.
