Re: [R] qq.loglogistic

From: Spencer Graves <spencer.graves_at_pdf.com>
Date: Mon 08 Aug 2005 - 05:58:11 EST

          I know of no such function. Some authors have described PP and QQ plots for a arbitrary distributions. I've experimented with PP plots and QQ plots for uniform, Student's t, chi-square and F distributions, but have not gotten much out of them. The uniform plots failed to show adequate detail close to 0 or 1. With the Student's t, chi-square, and F plots, the points in the tail were too far apart for me to easily judge what was happening.

          However, I regularly use normal probability plots. If I wanted to test a logistic fit, I might esimate the parameters, e.g. using "fitdistr" in library(MASS), then transform the data to probabilities using plogis, then further tranform the probabilities to normal scores using qnorm. The I would make a normal probability plot.

          If anyone else has relevant experience, whether consistent or conflicting with mine, I'd be pleased to hear about it.

          spencer graves

Petr Mandys wrote:

> Hi,
>
> is there any similar function in R to S function qq.loglogistic, which
> produces a Q-Q plot?
>
> Thanks a lot
>
> Pete
>
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Received on Mon Aug 08 06:06:30 2005

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