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factorial for bigger number in R

Hi if factorial(1536) is used in R, output is inf or nan How to find 1536! in R?

r
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written by vimlakany • vimlakany

This is a questions for CrossValidated, however as your question intrigued me, I had a look. If you run the code you suggest:

> factorial(1536)
[1] Inf
Warning message:
In factorial(1536) : value out of range in 'gammafn'

Any factorial >170 is too large a number, and it won't be computed.

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written by andrew.j.skelton73 andrew.j.skelton73

Perl to the rescue:

perl -MMath::BigInt -e 'print Math::BigInt->bfac(1536)'
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written by Jean-Karim Heriche Jean-Karim Heriche

factorial(1536) would be more than a google, so you couldn't even represent it in a 64 bit floating point number (or even close).

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written by Devon Ryan Devon Ryan

There are similar questions asked on the R mailing list and other forums. Try googling "r large factorial" or "r factorial inf". (If you can work in log space you can use lfactorial(x) instead)

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written by dariober dariober

Hello vimlakany!

We believe that this post does not fit the main topic of this site.

Not a bioinformatics question.

For this reason we have closed your question. This allows us to keep the site focused on the topics that the community can help with.

If you disagree please tell us why in a reply below, we'll be happy to talk about it.

Cheers!

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written by Michael Dondrup Michael Dondrup

There were many questions related to python and R in Biostars? Thats the reason I posted the above question here.

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written by vimlakany • vimlakany

Hi vimlakany, Biostars is a bioinformatics QA and certainly in bioinformatics we use R and python a lot. That is why you find a lot questions on this topic. However, we require that each question is specifically related to bioinformatics or computational biology, and that this relation has to be apparent and detailed in the question itself. Your question looks like a question on numeric analysis or computation.

Btw: you can use lfactorial to use lgamma instead of gamma and get the natural logarithm:

> exp(lfactorial( 170 ))
[1] 7.257416e+306
> factorial(170)
[1] 7.257416e+306
> factorial(1536)
[1] Inf
Warning message:
In factorial(1536) : value out of range in 'gammafn'
> lfactorial(1536)
[1] 9738.123
>
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written by Michael Dondrup Michael Dondrup

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