libstdc++-v3/testsuite/util/statistic/sample_variance.hpp

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 2, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License
  17 // along with this library; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  19 // MA 02111-1307, USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
  24 // file, or you compile this file and link it with other files to
  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  32
  33 // Permission to use, copy, modify, sell, and distribute this software
  34 // is hereby granted without fee, provided that the above copyright
  35 // notice appears in all copies, and that both that copyright notice
  36 // and this permission notice appear in supporting documentation. None
  37 // of the above authors, nor IBM Haifa Research Laboratories, make any
  38 // representation about the suitability of this software for any
  39 // purpose. It is provided "as is" without express or implied
  40 // warranty.
  41
  42 /**
  43  * @file sample_variance.hpp
  44  * Contains a function for calculating a sample variance
  45  */
  46
  47 #ifndef PB_DS_SAMPLE_VAR_HPP
  48 #define PB_DS_SAMPLE_VAR_HPP
  49
  50 #include <list>
  51 #include <numeric>
  52 #include <math.h>
  53 #include <iterator>
  54
  55 namespace __gnu_pbds
  56 {
  57   namespace test
  58   {
  59     namespace detail
  60     {
  61 #define PB_DS_VTYPE typename std::iterator_traits<It>::value_type
  62
  63       template<typename It>
  64       PB_DS_VTYPE
  65       sample_variance(It b, It e, PB_DS_VTYPE sm)
  66       {
  67         PB_DS_VTYPE ss = 0;
  68         size_t num_res = 0;
  69
  70         while (b != e)
  71           {
  72             const PB_DS_VTYPE d =* b - sm;
  73             ss += d*  d;
  74             ++num_res;
  75             ++b;
  76           }
  77
  78         if (num_res == 1)
  79           return 0;
  80
  81         return ::sqrt(ss / (num_res - 1));
  82       }
  83
  84 #undef PB_DS_VTYPE
  85
  86     } // namespace detail
  87   } // namespace test
  88 } // namespace __gnu_pbds
  89
  90 #endif
  91