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Diffstat (limited to 'gsl-1.9/randist/geometric.c')
-rw-r--r-- | gsl-1.9/randist/geometric.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/gsl-1.9/randist/geometric.c b/gsl-1.9/randist/geometric.c new file mode 100644 index 0000000..ce6c40d --- /dev/null +++ b/gsl-1.9/randist/geometric.c @@ -0,0 +1,67 @@ +/* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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 int +gsl_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; +} + +double +gsl_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; + } +} |