> -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of anna freni sterrantino > Sent: Tuesday, June 19, 2012 2:40 AM > To: Duncan Murdoch > Cc: Rcran help > Subject: Re: [R] inverse binomial in R > > > > Hi Duncan and Rlist, > I've notice a different behaviour in the invbinomial > you suggest me and invbinomial in stata. > > invbinomial(50,50, 0.4) > Error in uniroot(function(x) pbinom(k, n, x) - p, c(0, 1)) : > f() values at end points not of opposite sign > > invbinomial(50,50, 0.6) > Error in uniroot(function(x) pbinom(k, n, x) - p, c(0, 1)) : > f() values at end points not of opposite sign > > while stata > gen p3=invbinomial(50,50, 0.4) > > . display p3 > 0 > > > > > . gen p4=invbinomial(50,50, 0.6) > > . display p4 > 0 > > Thanks > Cheers > > Anna > > > ________________________________ > Da: Duncan Murdoch <murdoch.dun...@gmail.com> > > Cc: Rcran help <r-help@r-project.org> > Inviato: Giovedì 31 Maggio 2012 15:32 > Oggetto: Re: [R] inverse binomial in R > > On 12-05-31 9:10 AM, anna freni sterrantino wrote: > > Hello! > > I'm having some trouble > > trying to replicate in R a Stata function > > > > invbinomial(n,k,p) > > Domain n: 1 to 1e+17 > > Domain k: 0 to n - 1 > > Domain p: 0 to 1 (exclusive) > > Range: 0 to 1 > > Description: returns the inverse of the cumulative binomial; > i.e., it > > returns the probability of success on one > trial such > > that the probability of observing floor(k) > or fewer > > successes in floor(n) trials is p. > > > > I've found some hints on the web like > > > http://rwiki.sciviews.org/doku.php?id=guides:tutorials:regression:table > > > > I tried to replicate using qbinom > > the results obtained in > > > >> invbinomial(10,5, 0.5) > >> .54830584 > > > > but with no success. > > I don't think base R has a function like that, though some contributed > package probably does. If you're writing it yourself you'd need to use > uniroot or some other solver, e.g > > invbinomial <- function(n, k, p) { > uniroot(function(x) pbinom(5, 10, x) - p, c(0, 1)) > } > [[alternative HTML version deleted]]
Anna, Acccording to the excerpt of Stata documentation that you quote, k must be strictly less than n. So, Stata apparently does not return an error (or even a warning) when you supply an invalid input, but the R function does. How do the functions compare when you supply valid inputs? What do you want the R function to do when k equals n? Dan Daniel J. Nordlund Washington State Department of Social and Health Services Planning, Performance, and Accountability Research and Data Analysis Division Olympia, WA 98504-5204 ______________________________________________ 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.
