# [R] large factorials

molinar sky2k2 at hotmail.com
Thu Apr 23 16:00:59 CEST 2009

```Here is what I did:
library(rSymPy)
factorial.sympy <- function(n) sympy(paste("factorial(", n, ")"))
factorial.sympy(171)
[1]
"1241018070217667823424840524103103992616605577501693185388951803611996075221691752992751978120487585576464959501670387052809889858690710767331242032218484364310473577889968548278290754541561964852153468318044293239598173696899657235903947616152278558180061176365108428800000000000000000000000000000000000000000"
>
Which work perfectly.

Here is one of my summation functions:

sum1 <- function(l,u,t,i,n,w) {
+ v <- 0
+ for (m in 0 :w) {
+ v1 <- ((u^(1/2))*(l^(1/2))*t)^(i-n+2*m)
+ v2 <- (factorial.sympy(i-n+m))*(factorial.sympy(m))
+ v3 <- v1/v2
+ v <- v+v3
+ }
+ return(v)
+ }

sum1(1,2,10,80,3,80)
Error in (factorial.sympy(i - n + m)) * (factorial.sympy(m)) :
non-numeric argument to binary operator

I'm not sure why it works when I do the factorial normally but when I call
my function it doesn't work?

molinar wrote:
>
> Thank you everyone all of your posts were very helpful.  I tried each one
> and I think I have about 10 new packages installed.  The formula I need to
> calculate did not involve any logarithms but infinite summations of
> factorials, I'm sorry for not specifying.  I read some things about using
> logarithms but I thought in my case I would have to do an e to the log and
> by doing that R still gave me the same problems with numbers over 170.
>
> But I was able to get it to work by using the last post about the rsympy
> packages.
>
> I tried downloading bc but I didn't know how to connect it to R, so R said
> "could not find function bc".
>
> Thanks again for all of your help.
> Samantha
>
>
>
>
>
> Gabor Grothendieck wrote:
>>
>> Also the R sympy package can handle this:
>>
>>> library(rSymPy)
>>
>>> factorial.sympy <- function(n) sympy(paste("factorial(", n, ")"))
>>
>>> # note that first time sympy is called it loads java, jython and sympy
>>> # but on subsequent calls its faster.  So make a dummy call first.
>>> factorial.sympy(10)
>> [1] "3628800"
>>
>>> # code from earlier post defining factorial.bc to be inserted here
>>
>>>    benchmark(replications=10, columns=c('test', 'elapsed'),
>> +       bc=factorial.bc(500),
>> +       sympy = factorial.sympy(500))
>>    test elapsed
>> 1    bc    2.17
>> 2 sympy    0.09
>>
>>
>> On Wed, Apr 22, 2009 at 3:21 PM, molinar <sky2k2 at hotmail.com> wrote:
>>>
>>> I am working on a project that requires me to do very large factorial
>>> evaluations.  On R the built in factorial function and the one I created
>>> both are not able to do factorials over 170.  The first gives an error
>>> and
>>> mine return Inf.
>>>
>>> Is there a way to have R do these larger calculations (the calculator in
>>> accessories can do 10000 factorial and Maple can do even larger)
>>> --
>>> View this message in context:
>>> http://www.nabble.com/large-factorials-tp23175816p23175816.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
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>>>
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
>

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