LRgeom.c

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/*
 * Copyright    2019    R.K. Owen, Ph.D.
 * License      see lgpl.md (Gnu Lesser General Public License)
 */
#ifdef __cplusplus
extern "C" {
#endif

#include <math.h>
#include "libran.h"

/* int */
int LRi_geometric_RAN(LR_obj *o) {
        float zero = 0.0, one = 1.0, u, p = one;
        if (isnan(o->q))
                o->q = one/logf(one - o->p);

        do {
                u = o->uf(o);
        } while (u == zero);

        return ceilf(o->q * logf(u));
}

float LRi_geometric_PDF(LR_obj *o, int x) {
        float zero = 0.0, one = 1.0, p = o->p;

        if (x <= 0)     return zero;

        if (x == 1) {
                return p;
        } else {
                float q = one - p;
                for (int nn = 2; nn <= x; nn++) {
                        p *= q;
                }
                return p;
        }
}

float LRi_geometric_CDF(LR_obj *o, int x) {
        float zero = 0.0, one = 1.0, q = one - o->p, p = q;

        if (x <= 0)     return zero;

        if (x == 1) {
                return one - p;
        } else {
                for (int nn = 2; nn <= x; nn++) {
                        p *= q;
                }
                return one - p;
        }
}

#ifdef __cplusplus
}
#endif