mean_source.c

来自「math library from gnu」· C语言 代码 · 共 36 行

/* statistics/mean_source.c
 * 
 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Jim Davies, 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 3 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.
 */

double
FUNCTION (gsl_stats, mean) (const BASE data[], const size_t stride, const size_t size)
{
  /* Compute the arithmetic mean of a dataset using the recurrence relation 
     mean_(n) = mean(n-1) + (data[n] - mean(n-1))/(n+1)   */

  long double mean = 0;
  size_t i;

  for (i = 0; i < size; i++)
    {
      mean += (data[i * stride] - mean) / (i + 1);
    }

  return mean;
}