Hi I want to sample from a discrete random variable X, defined on the non-negative integers, with prob(X=0) = (1-p) prob(X=1) = (1-p)*p ... prob(X=i)=(1-p)*p^i ... Before reinventing the wheel, is there a ready-made R function to give me such a thing? -- Robin Hankin Uncertainty Analyst National Oceanography Centre, Southampton European Way, Southampton SO14 3ZH, UK tel 023-8059-7743
Hi, have a look at http://mathworld.wolfram.com/GeometricDistribution.html respectively http://mathworld.wolfram.com/NegativeBinomialDistribution.html with r = 1. In R have a look at ?rnbinom with n = 1 and in your case: prob = 1-p hth Matthias>Hi > >I want to sample from a discrete random variable X, defined on >the non-negative integers, with > >prob(X=0) = (1-p) >prob(X=1) = (1-p)*p >... >prob(X=i)=(1-p)*p^i >... > > > >Before reinventing the wheel, >is there a ready-made R function to give me such a thing? > > >-- >Robin Hankin >Uncertainty Analyst >National Oceanography Centre, Southampton >European Way, Southampton SO14 3ZH, UK > tel 023-8059-7743 > >______________________________________________ >R-help at stat.math.ethz.ch mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > >-- StaMatS - Statistik + Mathematik Service Dr. rer. nat. Matthias Kohl Gottlieb-Keim-Stra??e 60 95448 Bayreuth Phone: +49 921 50736457 E-Mail: matthias.kohl at stamats.de Home: www.stamats.de
On 23-Feb-06 Robin Hankin wrote:> Hi > > I want to sample from a discrete random variable X, defined on > the non-negative integers, with > > prob(X=0) = (1-p) > prob(X=1) = (1-p)*p > ... > prob(X=i)=(1-p)*p^i > ... > > > > Before reinventing the wheel, > is there a ready-made R function to give me such a thing?Use rgeom(n,(1-p)) Note (from ?rgeom) that these functions use the definition P(n) = p*(1-p)^n i.e. the complementary value of p to the one in your description. Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 23-Feb-06 Time: 09:18:50 ------------------------------ XFMail ------------------------------