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/* ------------------------------------------------------------- */
/* File: example2.c */
/* ------------------------------------------------------------- */
/* Include UNURAN header files. */
#include <unuran.h>
#include <unuran_urng_rngstreams.h>
/* ------------------------------------------------------------- */
int main(void)
{
int i; /* loop variable */
double x; int k; /* will hold the random number */
/* Declare UNU.RAN objects. */
UNUR_DISTR *distr; /* distribution object */
UNUR_PAR *par; /* parameter object */
UNUR_GEN *gen1, *gen2, *gen3; /* generator objects */
/* Declare objects for uniform random number generators. */
UNUR_URNG *urng2; /* uniform RN generator object */
/* -- Optional: Set seed for RNGSTREAMS library -------------- */
/* The RNGSTREAMS library sets a package seed. */
unsigned long seed[] = {111u, 222u, 333u, 444u, 555u, 666u};
RngStream_SetPackageSeed(seed);
/* -- Example 1 ---------------------------------------------- */
/* Beta distribution with shape parameters 2 and 3. */
/* Use method 'AUTO' (AUTOmatic). */
/* Create distribution object. */
{
double fparams[] = {2., 3.};
distr = unur_distr_beta( fparams, 2 );
}
/* Choose a method: 'AUTO'. */
par = unur_auto_new(distr);
/* Create the generator object. */
gen1 = unur_init(par);
/* It is important to check if the creation of the generator */
/* object was successful. Otherwise `gen1' is the NULL pointer */
/* and would cause a segmentation fault if used for sampling. */
if (gen1 == NULL) {
fprintf(stderr, "ERROR: cannot create generator object\n");
exit (EXIT_FAILURE);
}
/* It is possible to reuse the distribution object to create */
/* another generator object. If you do not need it any more, */
/* it should be destroyed to free memory. */
unur_distr_free(distr);
/* Now you can use the generator object `gen1' to sample from */
/* the target distribution. Eg.: */
for (i=0; i<10; i++) {
x = unur_sample_cont(gen1);
printf("%f\n",x);
}
/* -- Example 2 ---------------------------------------------- */
/* Student's t distribution with 3 degrees of freedom. */
/* Use method 'TDR' (Transformed Density Rejection) with */
/* "immediate acception" */
/* Create distribution object. */
{
double fparams[] = {3.};
distr = unur_distr_student( fparams, 1 );
}
/* Choose a method: 'TDR'. */
par = unur_tdr_new(distr);
/* ... and change to immediate acceptance. */
unur_tdr_set_variant_ia(par);
/* However, this time we use a (new) independent stream of */
/* uniformrandom numbers. */
urng2 = unur_urng_rngstream_new("urng2");
unur_set_urng( par, urng2 );
/* Create the generator object. */
gen2 = unur_init(par);
if (gen2 == NULL) exit (EXIT_FAILURE);
/* Destroy distribution object. (We do not need it any more.) */
unur_distr_free(distr);
/* Draw a sample. */
for (i=0; i<10; i++) {
x = unur_sample_cont(gen2); printf("%f\n",x);
}
/* -- Example 3 ---------------------------------------------- */
/* Discrete distribution with given probability vector. */
/* Use method 'DGT' (Discrete Guide Table method). */
/* Create distribution object. */
{
double probs[] = {0.5, 1.5, 1.0, 0.3};
distr = unur_distr_discr_new();
unur_distr_discr_set_pv(distr, probs, 4);
}
/* Choose a method: 'DGT'. */
par = unur_dgt_new(distr);
/* we use the default URNG again. So there is nothing to do. */
/* Create the generator object. */
gen3 = unur_init(par);
if (gen3 == NULL) exit (EXIT_FAILURE);
/* Destroy distribution object. (We do not need it any more.) */
unur_distr_free(distr);
/* Draw a sample. Notice that we get integers! */
for (i=0; i<10; i++) {
k = unur_sample_discr(gen3); printf("%d\n",k);
}
/* -- Call destructor ---------------------------------------- */
/* When generators are not needed any they can be destroyed. */
unur_free(gen1);
unur_free(gen2); unur_urng_free(urng2);
unur_free(gen3);
exit (EXIT_SUCCESS);
} /* end of main() */
/* ------------------------------------------------------------- */
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