source: trunk/c++_tools/statistics/tScore.h @ 669

Last change on this file since 669 was 669, checked in by Peter, 15 years ago

#closes #88. SAM score class added

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  • Property svn:keywords set to Author Date Id Revision
File size: 3.3 KB
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1#ifndef _theplu_statistics_tscore_
2#define _theplu_statistics_tscore_
3
4// $Id: tScore.h 669 2006-10-07 04:42:44Z peter $
5
6// C++ tools include
7/////////////////////
8#include <c++_tools/statistics/Score.h>
9
10#include <gsl/gsl_cdf.h>
11
12
13namespace theplu {
14  namespace utility {
15    class vector;
16  }
17namespace statistics { 
18
19  ///
20  /// Class for Fisher's t-test.
21  ///   
22  /// See <a href="http://en.wikipedia.org/wiki/Student's_t-test">
23  /// http://en.wikipedia.org/wiki/Student's_t-test</a> for more
24  /// details on the t-test.
25  ///
26  class tScore : public Score
27  {
28 
29  public:
30    ///
31    /// Default Constructor.
32    ///
33    tScore(bool absolute=true);
34
35   
36    /**
37       Calculates the value of t-score, i.e. the ratio between
38       difference in mean and standard deviation of this
39       difference. \f$ t = \frac{ m_x - m_y }
40       {s\sqrt{\frac{1}{n_x}+\frac{1}{n_y}}} \f$ where \f$ m \f$ is the
41       mean, \f$ n \f$ is the number of data points and \f$ s^2 =
42       \frac{ \sum_i (x_i-m_x)^2 + \sum_i (y_i-m_y)^2 }{ n_x + n_y -
43       2 } \f$
44       
45       @return t-score. If absolute=true absolute value of t-score
46       is returned
47    */
48    double score(const classifier::Target& target, 
49                 const utility::vector& value); 
50
51    /**
52       Calculates the weighted t-score, i.e. the ratio between
53       difference in mean and standard deviation of this
54       difference. \f$ t = \frac{ m_x - m_y }{
55       s\sqrt{\frac{1}{n_x}+\frac{1}{n_y}}} \f$ where \f$ m \f$ is the
56       weighted mean, n is the weighted version of number of data
57       points \f$ \frac{\left(\sum w_i\right)^2}{\sum w_i^2} \f$, and
58       \f$ s^2 \f$ is an estimation of the variance \f$ s^2 = \frac{
59       \sum_i w_i(x_i-m_x)^2 + \sum_i w_i(y_i-m_y)^2 }{ n_x + n_y - 2
60       } \f$. See AveragerWeighted for details.
61       
62       @return t-score. If absolute=true absolute value of t-score
63       is returned
64    */
65    double score(const classifier::Target& target, 
66                 const classifier::DataLookupWeighted1D& value); 
67
68    ///
69    /// Calculates the weighted t-score, i.e. the ratio between
70    /// difference in mean and standard deviation of this
71    /// difference. \f$ t = \frac{ m_x - m_y }{
72    /// \frac{s2}{n_x}+\frac{s2}{n_y}} \f$ where \f$ m \f$ is the
73    /// weighted mean, n is the weighted version of number of data
74    /// points and \f$ s2 \f$ is an estimation of the variance \f$ s^2
75    /// = \frac{ \sum_i w_i(x_i-m_x)^2 + \sum_i w_i(y_i-m_y)^2 }{ n_x
76    /// + n_y - 2 } \f$. See AveragerWeighted for details.
77    ///
78    /// @return t-score if absolute=true absolute value of t-score
79    /// is returned
80    ///
81    double score(const classifier::Target& target, 
82                 const utility::vector& value, 
83                 const utility::vector& weight); 
84
85    ///
86    /// Calculates the p-value, i.e. the probability of observing a
87    /// t-score equally or larger if the null hypothesis is true. If P
88    /// is near zero, this casts doubt on this hypothesis. The null
89    /// hypothesis is that the means of the two distributions are
90    /// equal. Assumtions for this test is that the two distributions
91    /// are normal distributions with equal variance. The latter
92    /// assumtion is dropped in Welch's t-test.
93    ///
94    /// @return the one-sided p-value( if absolute=true is used
95    /// the two-sided p-value)
96    ///
97    double p_value() const;
98
99         
100         
101  private:
102    double t_;
103    double dof_;
104       
105  };
106
107}} // of namespace statistics and namespace theplu
108
109#endif
110
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