[R] Non-central distributions

(Ted Harding) Ted.Harding at nessie.mcc.ac.uk
Thu Oct 17 17:24:31 CEST 2002

Hi Folks,

I note that, while the "chisq" functions

     dchisq(x, df, ncp=0, log = FALSE)
     pchisq(q, df, ncp=0, lower.tail = TRUE, log.p = FALSE)
     qchisq(p, df, ncp=0, lower.tail = TRUE, log.p = FALSE)
     rchisq(n, df, ncp=0)

all have a slot for the non-centrality parameter "ncp", of
the functions for the t and F distributions:

     dt(x, df, log = FALSE)
     pt(q, df, ncp=0, lower.tail = TRUE, log.p = FALSE)
     qt(p, df,        lower.tail = TRUE, log.p = FALSE)
     rt(n, df)

     df(x, df1, df2, log = FALSE)
     pf(q, df1, df2, ncp=0, lower.tail = TRUE, log.p = FALSE)
     qf(p, df1, df2,        lower.tail = TRUE, log.p = FALSE)
     rf(n, df1, df2)

only the CDF functions 'pt' and 'pf' allow this parameter to
be set. (If you try in the others, you get the message
"unused argument(s) (ncp ...)").

Why is this? Being able to set it would be just as useful ...

Thanks, and best wishes to all,
[and apologies if I should have been able to read the answer
for myself, somewhere ... ]

E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 167 1972
Date: 17-Oct-02                                       Time: 16:24:31
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