Sorry that I posted the wrong syntax. My initial program is very long
and I tried to post the section where I have been narrowed to locate the
problem.
In this sample I am simulating a Gamma with size parameter 5000 and
scale parameter 1.
I plugged in many breaks in my initial program and what I found was that
most of the time the program stops when encountering a call to rgamma()
function. It just freezes without popping out any error.
#include<Rmath.h>
#include<time.h>
#include<Rinternals.h>
SEXP generateGamma ()
{
SEXP a;
PROTECT(a=allocVector(REALSXP,1));
srand(time(NULL));
REAL(a)[0]=rgamma(5000,1);
UNPROTECT(1);
return (a);
}
Thanks for your suggestions!
On 07/15/12 07:07, peter dalgaard wrote:
On Jul 14, 2012, at 04:55 , Chandler Zuo wrote:
Hi,
Has anyone encountered the problem of rgamma function in C? The following
simplified program always dies for me, and I wonder if anyone can tell me the
reason.
#include<Rmath.h>
#include<time.h>
#include<Rinternals.h>
SEXP generateGamma ()
{
srand(time(NULL));
return (rgamma(5000,1));
}
Has anyone encountered a similar problem before? Is there another way of
generating Gamma random variable in C?
P.S. I have no problem compiling and loading this function in R.
It doesn't even give off a warning??
The prototype in Rmath.h is
double rgamma(double, double);
and you should be returning an SEXP. As soon as something tries to interpret
the double value as a pointer -- Poof!
Notice that rgamma in C is not the same function as the R counterpart, in
particular it isn't vectorized, so only generates one random number at a time.
The long and the short of it is that you need to read up on sections 5.9 and
5.10 of Writing R Extensions.
Thanks for suggestions in advance!
--Chandler
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and provide commented, minimal, self-contained, reproducible code.
