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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