> it gives 'NA' (for whatever y value). What 'y' values were you using? inf_f maps probabilities (in [0,1]) to values in the range of the orginal data, x, but it will have problems for a probability below 1/length(x) because the original data didn't tell you anything about the ecdf in that region.
> X <- c(101, 103, 107, 111) > f <- ecdf(X) > inv_f <- inv_ecdf(f) > inv_f(seq(0, 1, by=1/8)) [1] NA NA 101 102 103 105 107 109 111 Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of Manoranjan Muthusamy > Sent: Thursday, October 31, 2013 6:18 PM > To: Rui Barradas > Cc: r-help@r-project.org > Subject: Re: [R] Extracting values from a ecdf (empirical cumulative > distribution function) > curve > > Thank you, Barradas. It works when finding y, but when I tried to find x > using interpolation for a known y it gives 'NA' (for whatever y value). I > couldn't find out the reason. Any help is really appreciated. > > Thanks, > Mano > > > On Thu, Oct 31, 2013 at 10:53 PM, Rui Barradas <ruipbarra...@sapo.pt> wrote: > > > Hello, > > > > As for the problem of finding y given the ecdf and x, it's very easy, just > > use the ecdf: > > > > f <- ecdf(rnorm(100)) > > > > x <- rnorm(10) > > y <- f(x) > > > > If you want to get the x corresponding to given y, use linear > > interpolation. > > > > inv_ecdf <- function(f){ > > x <- environment(f)$x > > y <- environment(f)$y > > approxfun(y, x) > > } > > > > g <- inv_ecdf(f) > > g(0.5) > > > > > > Hope this helps, > > > > Rui Barradas > > > > Em 31-10-2013 12:25, Manoranjan Muthusamy escreveu: > > > >> Hi R users, > >> > >> I am a new user, still learning basics of R. Is there anyway to extract y > >> (or x) value for a known x (or y) value from ecdf (empirical cumulative > >> distribution function) curve? > >> > >> Thanks in advance. > >> Mano. > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________**________________ > >> R-help@r-project.org mailing list > >> https://stat.ethz.ch/mailman/**listinfo/r- > help<https://stat.ethz.ch/mailman/listinfo/r-help> > >> PLEASE do read the posting guide http://www.R-project.org/** > >> posting-guide.html <http://www.R-project.org/posting-guide.html> > >> and provide commented, minimal, self-contained, reproducible code. > >> > >> > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.
