Dear all,
in relation to your question, the following working paper of Leo Knuesel,
University of Munich, might be of interest:
"On the Accuracy of Statistical Distributions in S-Plus for Windows (1999)"
You can download the paper from (pdf-Format, 45k):
http://www.stat.uni-muenchen.de/~knuesel/elv/accuracy.html
Best,
Roland
> -----Original Message-----
> From: Spencer Graves [SMTP:spencer.graves@PDF.COM]
> Sent: Thursday, February 13, 2003 6:12 PM
> To: Jose María Fedriani Laffitte
> Cc: s-news@lists.biostat.wustl.edu
> Subject: Re: [S] Exact p-values
>
>
> Try ( 1-pchisq(29.8, df=1)): With S-Plus 6.1, I got 4.78992e-008.
>
> By the way, the distribtion functions in R have more arguments.
> For example, pchisq(29.8, df=1, lower.tail=F) produces the same
> answer, and pchisq(29.8, df=1, lower.tail=F, log=T) produces its natural
> logarithm. Also, pchisq, dchisq, qchisq, and rchisq in R all have an
> "ncp" noncentrality parameter argument; only pchisq has such in S-Plus
> 6.1. Similarly, none of the Student's t functions in S-Plus have a
> non-centralitity parameter; in R, pt has an argument ncp, and from this
> one can easily program ncp for dt, qt and rt. Also, the distribution
> functions in the current release of S-Plus are known to have problems.
> For example, pt(-1, Inf) = 0.5 in S-Plus 6.1, but 0.159 in R; clearly,
> S-Plus gives a wrong answer without warning.
>
> Best Wishes,
> Spencer Graves
>
> Jose María Fedriani Laffitte wrote:
>
> >Dear all,
> >
> > I want to get the exact p-values, on 1 degree of freedom, for an
> array
> >of chi-square values. When my chi-square values are equal or lower than
> >29.7, I get the exact associated p-values. Thus, for instance:
> >
> >
> >
> >>pchisq(29.7, df=1)
> >>
> >>
> >[1] 0.9999999
> >
> >However, when my chi-square values are greater or equal to 29.8 what I
> get
> >is:
> >
> >
> >
> >>pchisq(29.8, df=1)
> >>
> >>
> >[1] 1
> >
> >
> > Could anyone tell me how to fix this trivial issue? Very grateful,
> Jose
> >M. Fedriani
> >
> >****************************************
> >Jose Mª Fedriani Laffitte
> >Estacion Biologica de Donana (CSIC)
> >Avda. Mª Luisa s/n
> >41013-Sevilla
> >Spain
> >Tel. +34-954232340
> >Fax +34-954621125
> >http://ebd.csic.es
> >
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