1 /* statistics/median_source.c 2 * 3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Jim Davies, Brian Gough 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 3 of the License, or (at 8 * your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, but 11 * WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 * General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 18 */ 19 20 21 double 22 FUNCTION(gsl_stats,median_from_sorted_data) (const BASE sorted_data[], 23 const size_t stride, 24 const size_t n) 25 { 26 double median ; 27 const size_t lhs = (n - 1) / 2 ; 28 const size_t rhs = n / 2 ; 29 30 if (n == 0) 31 return 0.0 ; 32 33 if (lhs == rhs) 34 { 35 median = sorted_data[lhs * stride] ; 36 } 37 else 38 { 39 median = (sorted_data[lhs * stride] + sorted_data[rhs * stride])/2.0 ; 40 } 41 42 return median ; 43 } 44 45