[R] 'fitdistr' and two views of the same data?

From: Matt Jadud <jadudm_at_gmail.com>
Date: Thu 19 May 2005 - 00:34:57 EST


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



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