Re: [R] Inverse noncentral Beta

From: Ted Harding <ted.harding_at_wlandres.net>
Date: Sun, 03 Apr 2011 14:18:02 +0100 (BST)


On 03-Apr-11 13:03:30, Eduardo M. A. M.Mendes wrote:
> Hello
> I could not find whether there is any R-function that implements
> the inverse of a noncentral Beta. Could someone out there tell
> me where I can find it? Or how to implement it?
>
> Many thanks
> Ed

Have a look at the 'ncp' paramater in ?qbeta -- this (default=0) is the non-centrality parameter for the beta distribution, and qbeta is the inverse function of the distribution.

  The noncentral Beta distribution (with ?ncp? = lambda) is defined   (Johnson et al, 1995, pp. 502) as the distribution of X/(X+Y)   where X ~ chi^2_2a(lambda) and Y ~ chi^2_2b.

i.e. as in qbeta(p,a,b,ncp=lambda)

Hoping this helps,
Ted.



E-Mail: (Ted Harding) <ted.harding_at_wlandres.net> Fax-to-email: +44 (0)870 094 0861
Date: 03-Apr-11                                       Time: 14:17:58
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