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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2023 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 3, 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 COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20
  21 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  22
  23 // Permission to use, copy, modify, sell, and distribute this software
  24 // is hereby granted without fee, provided that the above copyright
  25 // notice appears in all copies, and that both that copyright notice
  26 // and this permission notice appear in supporting documentation. None
  27 // of the above authors, nor IBM Haifa Research Laboratories, make any
  28 // representation about the suitability of this software for any
  29 // purpose. It is provided "as is" without express or implied
  30 // warranty.
  31
  32 /**
  33  * @file sample_variance.hpp
  34  * Contains a function for calculating a sample variance
  35  */
  36
  37 #ifndef PB_DS_SAMPLE_VAR_HPP
  38 #define PB_DS_SAMPLE_VAR_HPP
  39
  40 #include <list>
  41 #include <numeric>
  42 #include <math.h>
  43 #include <iterator>
  44
  45 namespace __gnu_pbds
  46 {
  47   namespace test
  48   {
  49     namespace detail
  50     {
  51 #define PB_DS_VTYPE typename std::iterator_traits<It>::value_type
  52
  53       template<typename It>
  54       PB_DS_VTYPE
  55       sample_variance(It b, It e, PB_DS_VTYPE sm)
  56       {
  57         PB_DS_VTYPE ss = 0;
  58         size_t num_res = 0;
  59
  60         while (b != e)
  61           {
  62             const PB_DS_VTYPE d =* b - sm;
  63             ss += d*  d;
  64             ++num_res;
  65             ++b;
  66           }
  67
  68         if (num_res == 1)
  69           return 0;
  70
  71         return ::sqrt(ss / (num_res - 1));
  72       }
  73
  74 #undef PB_DS_VTYPE
  75
  76     } // namespace detail
  77   } // namespace test
  78 } // namespace __gnu_pbds
  79
  80 #endif
  81