Displaying 5 results from an estimated 5 matches for "logbeta".
2013 Feb 28
3
Negative Binomial Regression - glm.nb
Dear all,
I would like to ask, if there is a way to make the variance / dispersion parameter $\theta$ (referring to MASS, 4th edition, p. 206) in the function glm.nb dependent on the data, e.g. $1/ \theta = exp(x \beta)$ and to estimate the parameter vector $\beta$ additionally.
If this is not possible with glm.nb, is there another function / package which might do that?
Thank you very much for
2001 Dec 09
1
error in qbeta (PR#1201)
Full_Name: Ziheng Yang
Version: 1.3.1
OS: Windows 98
Submission from: (NULL) (172.136.54.89)
I noticed that qbeta is sometimes wrong and the error is not even due to the
beta parameters being too extreme. I am calculating the quantiles corresponding
to cdf = 0.05, 0.15, ..., 0.95. The value corresponding to cdf=0.25 is wrong
while all other values are correct.
qbeta(0.05, 0.143891, 0.05) =
1998 Oct 25
2
EGCS optimizer bug?
...l example of the problem (no, it doesn't do anything useful, and
there are several obvious things wrong with it, but it displays the
%ebx problem, if you look at the generated code):
#include <math.h>
double lbeta(){}
double qbeta(double alpha, double p, double q)
{
double t,r, logbeta;
volatile double xinbta;
logbeta = lbeta(p, q);
if (p<1)
t = r * pow(t, 3.);
return xinbta;
}
main(){qbeta(.5,.5,.5);}
[pd@butterfly sandbox]$ egcs -O qbeta.c -lm
[pd@butterfly sandbox]$ ./a.out
Segmentation fault (core dumped)
[pd@butterfly...
2003 Sep 22
2
PR#2894
...er. Just a close
>approximation.
...
>There are lots of other places that worry me with respect to cancellation
>errors, for example
>
> r = 1 - pp;
> t = 1 - qq;
These can also be removed by changing qbeta.c:156-157 (R-1.7.1)
to
y = (y-a) * xinbta * (1.0-xinbta) *
exp (logbeta - pp * log(xinbta) - qq * log1p(-xinbta));
I don't understand why you have qbeta.c:167
if (fabs(y)<=acu) goto L_converged
which will fail for certain values of p & q, when x is close to zero as
the beta density tends to infinity. Why not use an exit condition based on
how far away from...
2003 Nov 24
0
PR#2894
...er. Just a close
>approximation.
...
>There are lots of other places that worry me with respect to cancellation
>errors, for example
>
> r = 1 - pp;
> t = 1 - qq;
These can also be removed by changing qbeta.c:156-157 (R-1.7.1)
to
y = (y-a) * xinbta * (1.0-xinbta) *
exp (logbeta - pp * log(xinbta) - qq * log1p(-xinbta));
I don't understand why you have qbeta.c:167
if (fabs(y)<=acu) goto L_converged
which will fail for certain values of p & q, when x is close to zero as
the beta density tends to infinity. Why not use an exit condition based on
how far away f...