probs.c

来自「dbacl是一个通用目的的digramic贝叶斯文本分类器。它可以学习你提供的文」· C语言 代码 · 共 31 行

/* 
 * Copyright (C) 2002, 2003 Laird Breyer
 *  
 * 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.
 * 
 * Author:   Laird Breyer <[e-mail]>
 */

#include <math.h>

/* returns the logarithm of a Poisson distribution 
   (calculations based on Stirling's formula) */
double log_poisson(int k, double lambda) {

  return (double)k * (log(lambda) -log((double)k) + 1.0) - 
    log(2.0 * M_PI * (double)k ) / 2.0 - lambda;

}