Dear Lorenzo, Please do read the posting guide (https://www.r-project.org/posting-guide.html) : The ‘main’ R mailing list, for discussion about problems and solutions using R, about the availability of new functionality for R and documentation of R, comparison and compatibility with S-plus, and for the posting of nice examples and benchmarks.
For your problem, you could do something like this x <- rbeta(1000, 3, 3) dbeta2 <- function(x, shape, ...) dbeta(x, shape, shape, ...) pbeta2 <- function(q, shape, ...) pbeta(q, shape, shape, ...) library(fitdistrplus) fitdist(x, "beta2", start=list(shape=1/2)) x <- rbeta(1000, .3, .3) fitdist(x, "beta2", start=list(shape=1/2), optim.method="L-BFGS-B", lower=1e-2) Regards, Christophe --------------------------------------- Christophe Dutang LMM, UdM, Le Mans, France web: http://dutangc.free.fr > Le 23 mai 2017 à 18:22, Lorenzo Isella <lorenzo.ise...@gmail.com> a écrit : > > Dear All, > In principle it is a simple question, but not idea about how to tackle > it. > Suppose you have a distribution depending on two parameters, > e.g. beta(a,b). > For some reasons, you want to impose > that the two parameters of the beta distribution are identical, > i.e. you want to fit your data to beta(a,a). > For instance > > x<-rbeta(1000, 0.1, 0.1) > require(fitdistrplus) > > mm<-fitdist(x, "beta", method = "mge") > > > is how you would normally fit a sample, but I do not know how to > impose the constrain a=b before the fitting. > Any suggestion is appreciated. > Cheers > > Lorenzo ______________________________________________ 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.