[R] About 'choose' function
maechler at stat.math.ethz.ch
Mon Nov 8 22:49:49 CET 2004
>>>>> "Ted" == Ted Harding <Ted.Harding at nessie.mcc.ac.uk>
>>>>> on Mon, 08 Nov 2004 19:10:55 -0000 (GMT) writes:
Ted> On 08-Nov-04 Duncan Murdoch wrote:
>> On Mon, 08 Nov 2004 15:56:49 -0000 (GMT), (Ted Harding)
>> <Ted.Harding at nessie.mcc.ac.uk> wrote :
>>> Further investigation indicates that there is an integer
>>> truncation problem with 'choose':
>>> > print(choose(60000000000,1),digits=20) 
>>> 60001679906.00000 >
>>> print(my.choose3(60000000000,1),digits=20)  6e+10
>> Are you sure you're using the standard R choose()? I
>> get different results from you:
>>  6e+10
>> What platform are you using? I did this is Windows R
>> 2.0.0, and get the same result in the beta of 2.0.1.
Ted> Well, that's good to learn! As usual, I'm out of date,
Ted> but this time it seems to matter:
Ted> R-1.8.0 on Linux
Ted> (Yes, it was the standard R choose() from that
Ted> Perhaps I'd better roll up my sleeves and finally
Ted> upgrade (though I'm really waiting for the next release
Ted> since the move to 2.0 seems to have needed a few things
Ted> ironed out).
well, yes, but there are so many (mostly small) things that we
have ironed out in R since version 1.8.0....
The "NEWS" of 1.9.0 and 1.9.1 are already in file "ONEWS" (=
"Old News") and do contain
>> BUG FIXES
>> o [l]choose() use a more accurate formula which also slightly
>> improves p- and qhyper(); choose(n, k) now returns 0 instead
>> of NaN for k < 0 or > n.
Ted> Thanks for the cross-check, Duncan.
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