Note that the gamma distribution seems to work well here. After running Andy's code run this to see both superimposed on the same graph:
gparms <- fitdistr(dd, "gamma")[[1]] yyg <- dgamma(xx, gparms[1], gparms[2]) lines(xx, yyg, col=3) On 5/18/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > Matt, > > There is nothing wrong here. I rerun your example and got the same > parameters. Your only "problem" is that you let the density plot use the > default limits on x, which are not reasonable here since your data extends > to over 200. Try this: > > hist(dd, freq=FALSE) #dd is your original data > xx <- seq(0, 300, by=.1) > yy <- dweibull(xx, shape=1.5079, scale=60.2139) > lines(xx, yy, col=2) > > BTW, when you binned your data you also scaled it down by 20, so your scale > parameter changed accordingly. > > Cheers, > > Andy > > __________________________________ > Andy Jaworski > 518-1-01 > Process Laboratory > 3M Corporate Research Laboratory > ----- > E-mail: [EMAIL PROTECTED] > Tel: (651) 733-6092 > Fax: (651) 736-3122 > > Matt Jadud > <[EMAIL PROTECTED] > > To > Sent by: [email protected] > [EMAIL PROTECTED] cc > at.math.ethz.ch > Subject > [R] 'fitdistr' and two views of the > 05/18/2005 09:34 same data? > AM > > Please respond to > Matt Jadud > <[EMAIL PROTECTED] > > > > Hello, > > I have detailed (with pictures and whatnot) my question on my weblog at > > http://www.cs-ed.org/blogs/mjadud/archives/2005/05/a_question_abou.html > > The short version of the question is this: > > When I ask 'fitdistr' to try and fit my distribution as a "weibull" > distribution, it comes up with some rather wacky parameters. > > If I take the same distribution, and do something like > > newdist <- mapply(function(x) ((x %/% 20) + 1), origdist) > > which effectively forces the data into a histogram, 'fitdist' on > 'newdist' gives me an entirely different set of parameters. > Distressingly, the parameters it gives me are, upon inspection, good; > that is, the parameters reported fit the distribution of the original > data much better than 'fitdist' of 'origdist'. > > Unfortunately, I'm not savvy enough to tease this out beyond > "inspection." The weblog entry has the original distribution, plots, > and whatnot explaining my question in more detail. My question(s) are > repeated at the bottom of the post, as well as this email address. Any > help or insights are appreciated; no doubt, I've done something... > well, wrong. > > Many thanks, > Matt > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
