[R] BUG: choose function

[Duncan Murdoch]

On 22/11/2007 8:11 PM, Benilton Carvalho wrote:
> well,
> 
> choose(n, k) should actually return:
> 
> factorial(n)/(factorial(n-k)*factorial(k))

That's not how the docs define it.  They say

Note that 'choose(n,k)' is defined for all
      real numbers n and integer k.  For k >= 1 as n(n-1)...(n-k+1) /
      k!, as 1 for k = 0 and as 0 for negative k.

which agrees with your definition only for 0 <= k <= n.

Duncan Murdoch

> 
> R-2.6.0 works just fine for me.... so does R-2.5.1.... so does  
> R-2.4.1....
> 
> b
> 
> On Nov 22, 2007, at 8:04 PM, Luis Salasar wrote:
> 
>> Hi,
>>
>>  I have used the function choose(n, k) sometimes, and i realized  
>> that it doesn't work properly for n < 0. For example, if one tries  
>> choose(-1, 3), it should be returned the value (-1)^3 = -1, since  
>> choose (-1, 3) = (-1)*(-2)*(-3)/3! = (-1)^3, but indeed R returns  
>> the value 0. I am using R version 2.5.1, it don't know if this  
>> little bug has already been solved in the new version. Thanks,
>>
>>  Luis Ernesto.
>>
>>
>> ---------------------------------
>>
>> 	[[alternative HTML version deleted]]
>>
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> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.