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/* pdtr.c
*
* Poisson distribution
*
*
*
* SYNOPSIS:
*
* int k;
* double m, y, pdtr();
*
* y = pdtr( k, m );
*
*
*
* DESCRIPTION:
*
* Returns the sum of the first k terms of the Poisson
* distribution:
*
* k j
* -- -m m
* > e --
* -- j!
* j=0
*
* The terms are not summed directly; instead the incomplete
* Gamma integral is employed, according to the relation
*
* y = pdtr( k, m ) = igamc( k+1, m ).
*
* The arguments must both be nonnegative.
*
*
*
* ACCURACY:
*
* See igamc().
*
*/
/* pdtrc()
*
* Complemented poisson distribution
*
*
*
* SYNOPSIS:
*
* int k;
* double m, y, pdtrc();
*
* y = pdtrc( k, m );
*
*
*
* DESCRIPTION:
*
* Returns the sum of the terms k+1 to infinity of the Poisson
* distribution:
*
* inf. j
* -- -m m
* > e --
* -- j!
* j=k+1
*
* The terms are not summed directly; instead the incomplete
* Gamma integral is employed, according to the formula
*
* y = pdtrc( k, m ) = igam( k+1, m ).
*
* The arguments must both be nonnegative.
*
*
*
* ACCURACY:
*
* See igam.c.
*
*/
/* pdtri()
*
* Inverse Poisson distribution
*
*
*
* SYNOPSIS:
*
* int k;
* double m, y, pdtr();
*
* m = pdtri( k, y );
*
*
*
*
* DESCRIPTION:
*
* Finds the Poisson variable x such that the integral
* from 0 to x of the Poisson density is equal to the
* given probability y.
*
* This is accomplished using the inverse Gamma integral
* function and the relation
*
* m = igamci( k+1, y ).
*
*
*
*
* ACCURACY:
*
* See igami.c.
*
* ERROR MESSAGES:
*
* message condition value returned
* pdtri domain y < 0 or y >= 1 0.0
* k < 0
*
*/
/*
* Cephes Math Library Release 2.3: March, 1995
* Copyright 1984, 1987, 1995 by Stephen L. Moshier
*/
#include "mconf.h"
double pdtrc(k, m)
int k;
double m;
{
double v;
if ((k < 0) || (m < 0.0)) {
mtherr("pdtrc", DOMAIN);
return (NPY_NAN);
}
if (m == 0.0) {
return 0.0;
}
v = k + 1;
return (igam(v, m));
}
double pdtr(k, m)
int k;
double m;
{
double v;
if ((k < 0) || (m < 0.0)) {
mtherr("pdtr", DOMAIN);
return (NPY_NAN);
}
if (m == 0.0) {
return 1.0;
}
v = k + 1;
return (igamc(v, m));
}
double pdtri(k, y)
int k;
double y;
{
double v;
if ((k < 0) || (y < 0.0) || (y >= 1.0)) {
mtherr("pdtri", DOMAIN);
return (NPY_NAN);
}
v = k + 1;
v = igamci(v, y);
return (v);
}
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