[Rd] Bug on log.p argument with all stat function (PR#7420)
ligges at statistik.uni-dortmund.de
ligges at statistik.uni-dortmund.de
Tue Dec 14 13:11:04 CET 2004
casadoj at ecc.es wrote:
> Dear R Developers:
>
> I have been playing with R, release 2.0.1 for a week now and have detected =
> that all stat functions related to distribution probabilities have the same=
> problem:
>
> 1.- The log.p parameter of all distribution functions, when set to TRUE, re=
> turns a extrange value.
>
> Accoding to the manual, when set to true, it should return log(p) probabili=
> ty. So to my understanding, setting to true this parameters is the same as =
> getting the LOG of the same function with this parameter set to false.
>
>
>>pt (1.1, 5, F, T)
>
> [1] 0.8392746
>
>>pt (1.1, 5, T, T)
>
> [1] 0.5168608
>
>>log(pt (1.1, 5, F, T))
>
> [1] -0.1752173
>
> 1.- The first line is the lower tail cumulative probability of a 1.1 on a S=
> tudent T distribution with 5 degrees of freedom.
> 2.- The second line is the lower tail cumulative probability of a 1.1 on a =
> Student T distribution with 5 degrees of freedom on a log scale
> 3.- The third line is the same as the second, but calculated mannually inst=
> ead of using the log.p parameters
>
> Why line 2 and 3 do not return the same result?
Please NEVER submit bug reports twice, in particular not an unsensible one!
One time ncp = 1, one time ncp = 0, so what's that surprising?
Uwe Ligges
> Reciba un cordial saludo,
> =0D
> Jos=E9 Luis Casado Mart=EDnez
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