double ranbeta(double a, double b)
{
double xa, xb ;
if ((a<=0.0) || (b<=0.0)) fatalx("(ranbeta) bad parameters: %9.3f %9.3f\n", a, b) ;
xa = rangam(a) ;
xb = rangam(b) ;
return xa/(xa+xb) ;
}
double ranchi (int d)
{
double y ;
y = 2.0 * rangam(0.5 * (double) d) ;
return y ;
}
void randirichlet(double *x, double *pp, int n)
/**
generate dirichlet r.v. parameters pp
*/
{
double y ;
int i ;
for (i=0; i<n; i++) {
x[i] = rangam(pp[i]) ;
}
bal1(x,n) ;
}
double rant(double df)
// t distribution df > 0
{
static double p = -1, olddf = -1.0 ;
static double zkon ;
double y ;
if (df <=- 0.0) fatalx("(rant) %9.3f\n") ;
p = df/2.0 ;
zkon = sqrt(p) ; // variance of t is p/(p-1) if p > 1
y = rangam(p) ;
if (y==0.0) y = p ; // special case to avoid overflow ;
return gauss() * zkon / sqrt(y) ;
}
void randirichlet(double *x, double *pp, int n)
/**
generate dirichlet r.v. parameters pp
*/
{
int i ;
vzero(x, n) ;
for (i=0; i<n; i++) {
if (pp[i] > 0.0) {
x[i] = rangam(pp[i]) ;
}
}
bal1(x,n) ;
}
double gds( double a)
{
return rangam(a) ;
}
