The following one-liner generates uniformly distributed 3-tuples that sum to 1:
diff(c(0, sort(runif(2)), 1)) More, generally you can generate n-tuples that sum to unity as: diff(c(0, sort(runif(n-1)), 1)) Ravi. ____________________________________________________________________ Ravi Varadhan, Ph.D. Assistant Professor, Division of Geriatric Medicine and Gerontology School of Medicine Johns Hopkins University Ph. (410) 502-2619 email: rvarad...@jhmi.edu ----- Original Message ----- From: Greg Snow <greg.s...@imail.org> Date: Tuesday, March 29, 2011 1:02 pm Subject: Re: [R] Creating 3 vectors that sum to 1 To: Christopher Desjardins <cddesjard...@gmail.com>, "r-help@r-project.org" <r-help@r-project.org> > Do a search for Dirichlet, that may give you the tools you need. Also > for plotting 3 vectors that sum to 1, instead of a 3d scatter plot you > should look into a triangle or trilinear plot, see ?triplot in the > TeachingDemos package (the see also for that help page lists several > other implementations in other packages as well). > > -- > 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 [ > > project.org] On Behalf Of Christopher Desjardins > > Sent: Tuesday, March 29, 2011 10:20 AM > > To: r-help@r-project.org > > Subject: [R] Creating 3 vectors that sum to 1 > > > > I have 3 vectors: p1, p2, and p3. I would like each vector to be any > > possible value between 0 and 1 and p1 + p2 + p3 = 1. I want to graph > > these > > and I've thought about using scatterplot3d(). Here's what I have so > > far. > > > > library(scatterplot3d) > > p1 <- c(1,0,0,.5,.5,0,.5,.25,.25,.34,.33,.33,.8,.1,.1,.9,.05,.05) > > p2 <- c(0,1,0,.5,0,.5,.25,.5,.25,.33,.34,.33,.1,.8,.1,.05,.9,.05) > > p3 <- c(0,0,1,0,.5,.5,.25,.25,.5,.33,.33,.34,.1,.1,.8,.05,.05,.9) > > scatterplot3d(p1,p2,p3) > > > > > > However, I wonder if there is an easy way to create vectors p1, p2, > and > > p3. > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org mailing list > > > > PLEASE do read the posting guide > > guide.html > > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > > PLEASE do read the posting guide > 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.
