/* randist/geometric.c *  * Copyright (C) 1996, 1997, 1998, 1999, 2000 James Theiler, Brian Gough *  * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or (at * your option) any later version. *  * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * General Public License for more details. *  * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */#include <config.h>#include <math.h>#include <gsl/gsl_rng.h>#include <gsl/gsl_randist.h>/* Geometric distribution (bernoulli trial with probability p)    prob(k) =  p (1 - p)^(k-1) for n = 1, 2, 3, ...   It gives the distribution of "waiting times" for an event that   occurs with probability p. */unsigned intgsl_ran_geometric (const gsl_rng * r, const double p){  double u = gsl_rng_uniform_pos (r);  unsigned int k;  if (p == 1)    {      k = 1;    }  else    {      k = log (u) / log (1 - p) + 1;    }  return k;}doublegsl_ran_geometric_pdf (const unsigned int k, const double p){  if (k == 0)    {      return 0 ;    }  else if (k == 1)    {      return p ;    }  else    {      double P = p * pow (1 - p, k - 1.0);      return P;    }}