> On May 3, 2017, at 11:43 PM, Collins Ochieng Onyanga <coll...@aims.ac.tz> > wrote: > > Hi, > > I would like to fit a non standard beta distribution with the two scale > parameters and lower and upper boundaries to data like the one shown without > normalizing it. > [1] 37.50 46.79 48.30 46.04 43.40 39.25 38.49 49.51 40.38 36.98 40.00 > [12] 38.49 37.74 47.92 44.53 44.91 44.91 40.00 41.51 47.92 36.98 43.40 > [23] 42.26 41.89 38.87 43.02 39.25 40.38 42.64 36.98 44.15 44.91 43.40 > [34] 49.81 38.87 40.00 52.45 53.13 47.92 52.45 44.91 29.54 27.13 35.60 > > I have tried using the following code; > > fitdist((Z1-r)/(t-r) , "beta", method = "mme",lower=c(0,0)) > > but with this I am normalizing the data to be in the interval (0,1) .
So what's wrong with using that approach? If you try to re-invent the wheel, you will lose efficiency since dbata, qbeta and pbeta are all coded in C. Is the back-transformation difficult? The help page for fitdistrplus::fitdist has a worked example of defining a three-member dpq-distribution family. Admittedly the mathematical expression for the more general presented at the NIST document is mildly complex, but this now appears to be a request to satisfy a homework assignment. I never took a math-stats course, but this task doesn't appear particularly difficult, only tedious. And the Posting Guide says rhelp is not for homework. That rule would probably be relaxed if you showed greater effort at creating a 3 member set of gbeta distribution function, but I haven't seen that level of effort yet. -- David. > > > Thanks. > > On 4 May 2017 at 03:27, David Winsemius <dwinsem...@comcast.net> wrote: > > > On May 3, 2017, at 3:55 PM, Collins Ochieng Onyanga <coll...@aims.ac.tz> > > wrote: > > > > On 4 May 2017 at 01:00, Collins Ochieng Onyanga <coll...@aims.ac.tz> wrote: > > > >> Hi, > >> > >> I am trying to fit fit a non standard Beta distribution to a data set but > >> so far I have not succeeded. Can anyone help me with a code in R that can > >> do this. > >> > >> Thanks. > > > To Collins Ochieng Onyanga; > > David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
