WilDscOp <[EMAIL PROTECTED]> wrote: > Can anyone please help me about any of the following questions: > -------------------------------------------- > 1. How can i find "factorial" of any number in R? I tried > > prod(170:1) # to find factorial of 170 or 170! > Is it the only procedure - or R has any better process / operational > character to calculate factorial? Also, is it possible to calculate > factorial of 500? Or is there any statistical table available for this?
> gamma(x+1) # gives x! As for the factorial of 500, I would go for a log transformation: > lgamma(501) [1] 2611.330 But if you really need to see all the digits of 500!, PARI <http://pari.math.u-bordeaux.fr/> --or rather its shell, may be called from within R. It returns all digits of that large number in a fraction of a second on my old laptop: > system.time(system("echo '500!' | gp")) [...] %1 = 12201368259911100687012387854230469262535743428031928421 9241358838584537315388199760549644750220328186301361647714820 [about a thousand other digits follow] Good bye! [1] 0.00 0.00 0.05 0.03 0.02 For a more readable output: > system("echo '500!*1.0' | gp") [...] %1 = 1.220136825991110068701238785 E1134 > -------------------------------------------- > 2. Is there any direct procedure / package in R to find "permutation / > combination"? To permute the elements of a vector, you may use: > perm <- function(v)sample(v,size=length(v),replace=FALSE) > v <- 1:8 > v [1] 1 2 3 4 5 6 7 8 > set.seed(101) > perm(v) [1] 3 1 5 4 7 6 2 8 Re combinations, does the function choose() do what you are looking for? > -------------------------------------------- > 3. Can i find Probability Density of "Hypergeometric Disribution" in R, > given all values of the parameter? I can not find any table of > Hypergeometric Disribution (if such tables are available on the internet, > please let me know). Does dhyper() do what you are looking for? -- Philippe Glaziou Epidemiologist ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help