Dear Frede, the initial question was to find probability proportional to the values, so Rui, Dan and Boris are right...
I think I will go for Boris' solution... best regards, Simone 2014-04-11 7:29 GMT+02:00 Frede Aakmann Tøgersen <fr...@vestas.com>: > I think you have calculated the wrong probabilities. Shouldn't it be > >> x <- c(2,2,6,2,1,1,1,3) >> MASS::fractions(table(x)/length(x)) > x > 1 2 3 6 > 3/8 3/8 1/8 1/8 >> > > Yours sincerely / Med venlig hilsen > > > Frede Aakmann Tøgersen > Specialist, M.Sc., Ph.D. > Plant Performance & Modeling > > Technology & Service Solutions > T +45 9730 5135 > M +45 2547 6050 > fr...@vestas.com > http://www.vestas.com > > Company reg. name: Vestas Wind Systems A/S > This e-mail is subject to our e-mail disclaimer statement. > Please refer to www.vestas.com/legal/notice > If you have received this e-mail in error please contact the sender. > > >> -----Original Message----- >> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] >> On Behalf Of Nordlund, Dan (DSHS/RDA) >> Sent: 10. april 2014 22:04 >> To: Simone Gabbriellini; Rui Barradas >> Cc: r-help@r-project.org >> Subject: Re: [R] how to select an element from a vector based on a >> probability >> >> > -----Original Message----- >> > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- >> > project.org] On Behalf Of Simone Gabbriellini >> > Sent: Thursday, April 10, 2014 11:59 AM >> > To: Rui Barradas >> > Cc: r-help@r-project.org >> > Subject: Re: [R] how to select an element from a vector based on a >> > probability >> > >> > Hello, Rui, >> > >> > it does, indeed! >> > >> > thanks, >> > Simone >> > >> > 2014-04-10 20:55 GMT+02:00 Rui Barradas <ruipbarra...@sapo.pt>: >> > > Hello, >> > > >> > > Use ?sample. >> > > >> > > sample(x, 1, prob = x) >> > > >> >> Just be aware that, in using this method, the probability of selection of a >> particular value will also be a function of how frequent the value is. For >> example, >> >> set.seed(7632) >> x <- c(2,2,6,2,1,1,1,3) >> table(sample(x, 10000, prob=x, replace=TRUE)) >> >> 1 2 3 6 >> 1664 3340 1696 3300 >> >> >> The probability that a vector position with a value of 1 will be selected is >> 1/18 >> (in this particular example). However, the probability that a value of 1 >> will be >> selected is 1/6 since there are three 1's. The probability of selecting the >> position with a value of 3 is 3/18. But since there is only one position >> with a >> value of 3, the probability of getting the value 1 on any given sample is >> equal >> to the probability of getting the value 3. >> >> >> >> >> > > Hope this helps, >> > > >> > > Rui Barradas >> > > >> > > Em 10-04-2014 19:49, Simone Gabbriellini escreveu: >> > > >> > >> Hello List, >> > >> >> > >> I have an array like: >> > >> >> > >> c(4, 3, 5, 4, 2, 2, 2, 4, 2, 6, 6, 7, 5, 5, 5, 10, 10, 11, 10, >> > >> 12, 10, 11, 9, 12, 10, 36, 35, 36, 36, 36, 35, 35, 36, 37, 35, >> > >> 35, 38, 35, 38, 36, 37, 36, 36, 37, 36, 35, 35, 36, 36, 35, 35, >> > >> 36, 35, 38, 35, 35, 35, 36, 35, 35, 35, 6, 5, 8, 6, 6, 7, 1, >> > >> 7, 7, 8, 9, 7, 8, 7, 7, 13, 13, 13, 14, 13, 13, 13, 14, 14, 15, >> > >> 15, 14, 13, 14, 39, 39, 39, 39, 39, 39, 41, 40, 39, 39, 39, 39, >> > >> 40, 39, 39, 41, 41, 40, 39, 40, 41, 40, 41, 40, 40, 40, 39, 41, >> > >> 39, 39, 39, 39, 40, 39, 39, 40, 40, 39, 39, 39, 1, 4, 3, 4) >> > >> >> > >> I would like to pick up an element with a probability proportional >> > to >> > >> the element value, thus higher values should be picked up more often >> > >> than small values (i.e., picking up 38 should be more probable than >> > >> picking up 3) >> > >> >> > >> Do you have any idea on how to code such a rich-get-richer >> > mechanism? >> > >> >> > >> Best regards, >> > >> Simone >> > >> >> > > >> > >> > >> > >> >> Dan >> >> Daniel J. Nordlund, PhD >> Research and Data Analysis Division >> Services & Enterprise Support Administration >> Washington State Department of Social and Health Services >> >> >> ______________________________________________ >> 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. -- ----------------------------------------------------------------- Simone Gabbriellini, PhD Post-doctoral Researcher ANR founded research project "DIFFCERAM" GEMASS, CNRS & Paris-Sorbonne. mobile: +39 340 39 75 626 email: simone.gabbriell...@cnrs.fr ______________________________________________ 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.
