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mahalanobis.cc
1 // Copyright (C) 2009 EPITA Research and Development Laboratory (LRDE)
2 //
3 // This file is part of Olena.
4 //
5 // Olena is free software: you can redistribute it and/or modify it under
6 // the terms of the GNU General Public License as published by the Free
7 // Software Foundation, version 2 of the License.
8 //
9 // Olena is distributed in the hope that it will be useful,
10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 // General Public License for more details.
13 //
14 // You should have received a copy of the GNU General Public License
15 // along with Olena. If not, see <http://www.gnu.org/licenses/>.
16 //
17 // As a special exception, you may use this file as part of a free
18 // software project without restriction. Specifically, if other files
19 // instantiate templates or use macros or inline functions from this
20 // file, or you compile this file and link it with other files to produce
21 // an executable, this file does not by itself cause the resulting
22 // executable to be covered by the GNU General Public License. This
23 // exception does not however invalidate any other reasons why the
24 // executable file might be covered by the GNU General Public License.
25 
26 #include <cstdlib>
27 #include <mln/accu/stat/var.hh>
28 #include <mln/fun/stat/mahalanobis.hh>
29 
30 
31 float my_rand(int c)
32 {
33  return (1 + c) * float(std::rand()) / RAND_MAX;
34 }
35 
36 
37 int main()
38 {
39  using namespace mln;
40 
41  typedef algebra::vec<3,float> vec3f;
42 
43  enum { n = 1000 };
44  vec3f v[n];
45 
46  for (int i = 0; i < n; ++i)
47  {
48  v[i][0] = my_rand(0);
49  v[i][1] = my_rand(1);
50  v[i][2] = my_rand(2);
51  }
52 
54  for (int i = 0; i < n; ++i)
55  a.take(v[i]);
56 
57  fun::stat::mahalanobis<vec3f> f(a.variance(), a.mean());
58  mln_assertion(f(a.mean()) == 0.f);
59 
60  float sum = 0.f;
61  for (int i = 0; i < n; ++i)
62  {
63  float f_ = f(v[i]);
64  sum += f_ * f_;
65  }
66  mln_assertion(std::abs(sum / n - 3.f) < 0.00002f);
67 }