>>>>> "PD" == p dalgaard
<p.dalgaard@biostat.ku.dk> writes:
PD> Kenneth Cabrera <krcabrer@epm.net.co> writes:
>> Hello developers and users:
>>
>> My system fails (the computer freezes) when I use the ncp
parameter,
>> with the lower.tail=FALSE option in the qchisq function.
>>
>> qchisq(0.025,31,ncp=1,lower.tail=FALSE)
PD> Yup, that's a bug. We have in pnchisq.c
PD> 48 for (ux = 1.0; pnchisq(ux, n, lambda, lower_tail, log_p) < p;
PD> ux *= 2);
PD> 49 for (lx = ux; pnchisq(lx, n, lambda, lower_tail, log_p) > p;
PD> lx *= 0.5);
PD> but if we look at the opposite tail, we also need to reverse that
PD> logic since pnchisq(x,...) is now decreasing in x. Otherwise the
PD> algorithm will get stuck in one of the for loops.
Now fixed for R-devel (to become 1.3.0), together with the "FIXME"
comment
a few lines above.
Martin Maechler <maechler@stat.math.ethz.ch>
http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum LEO D10 Leonhardstr. 27
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1228 <><
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