[R] does a factorial function exist
Venables, Bill (CMIS, Cleveland)
Bill.Venables at cmis.CSIRO.AU
Thu Jun 24 02:14:08 CEST 1999
Two people now have essentially suggested
factorial <- function(n) prod(1:n)
as a possible factorial function. (One is included below.) I think it is
important to realise why this is NOT a good suggestion. In a nutshell: it
is not a vectorized solution. You may have only scalar arguments in mind
for the factorial function, but other users may not, (and the consensus view
is on their side.) Also, it doesn't work for n=0 but that's a lesser
Consider, for example
* n <- 0:5
 1 1 2 6 24 120
In writing functions for R or in using the system generally it is important
to make as much use as possible of vectorization for efficiency. This is
one aspect of what John Chambers calls "taking the `whole object' view" and
is the key to using systems like R effectively.
(Here endeth the sermon).
On Wed, 23 Jun 1999, Alex Buerkle wrote:
> I've looked through the documentation with R-0.64.1 and have been unable
> to find a high-level function for evaluation of factorials (i.e., n!, not
> factorial designs). Is there such a function?
Bill Venables, Statistician, CMIS Environmetrics Project.
Physical address: Postal address:
CSIRO Marine Laboratories, PO Box 120,
233 Middle St, Cleveland, Queensland Cleveland, Qld, 4163
Telephone: +61 7 3826 7251
Fax: +61 7 3826 7304 Email: Bill.Venables at cmis.csiro.au
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