1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2020 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
sample_variance(It b,It e,PB_DS_VTYPE sm)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 
82