On Oct 13, 2015, at 2:42 PM, Aditya Bhatia wrote: > I am trying to fit this data to a weibull distribution: > > My y variable is:1 1 1 4 7 20 7 14 19 15 18 3 4 1 3 1 1 1 > 1 1 1 1 1 1 > > and x variable is:1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 > 19 20 21 22 23 24 > > The plot looks like this:http://i.stack.imgur.com/FrIKo.png and I want > to fit a weibull curve to it. I am using the nls function in R like > this: nls(y ~ ((a/b) * ((x/b)^(a-1)) * exp(- (x/b)^a)))
So despite the fact that the Weibull function has a continuous domain, you want to fit a set of integers to something like the Weibull with these values as case weights with the "x-values" being the position of these integers in a sequence? -- David. > > This function always throws up an error saying: Error in > numericDeriv(form[[3L]], names(ind), env) : > Missing value or an infinity produced when evaluating the model > In addition: Warning message: > In nls(y ~ ((a/b) * ((x/b)^(a - 1)) * exp(-(x/b)^a))) : > No starting values specified for some parameters. > Initializing ‘a’, ‘b’ to '1.'. > Consider specifying 'start' or using a selfStart model > > So first I tried different starting values without any success. I > cannot understand how to make a "good" guess at the starting values. > Then I went with the SSweibull(x, Asym, Drop, lrc, pwr) function which > is a selfStart function. Now the SSWeibull function expects values for > Asym,Drop,lrc and pwr and I don't have any clue as to what those > values might be. > > I would appreciate if someone could help me figure out how to proceed. > > Background of the data: I have taken some data from bugzilla and my > "y" variable is number of bugs reported in a particular month and "x" > variable is the month number after release. > > ______________________________________________ > 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. 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.
