1 | #ifndef _theplu_statistics_tscore_ |
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2 | #define _theplu_statistics_tscore_ |
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3 | |
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4 | // $Id: tScore.h 675 2006-10-10 12:08:45Z jari $ |
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5 | |
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6 | /* |
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7 | Copyright (C) The authors contributing to this file. |
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8 | |
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9 | This file is part of the yat library, http://lev.thep.lu.se/trac/yat |
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10 | |
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11 | The yat library is free software; you can redistribute it and/or |
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12 | modify it under the terms of the GNU General Public License as |
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13 | published by the Free Software Foundation; either version 2 of the |
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14 | License, or (at your option) any later version. |
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15 | |
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16 | The yat library is distributed in the hope that it will be useful, |
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17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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19 | General Public License for more details. |
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20 | |
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21 | You should have received a copy of the GNU General Public License |
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22 | along with this program; if not, write to the Free Software |
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23 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA |
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24 | 02111-1307, USA. |
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25 | */ |
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26 | |
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27 | #include "yat/statistics/Score.h" |
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28 | |
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29 | #include <gsl/gsl_cdf.h> |
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30 | |
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31 | |
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32 | namespace theplu { |
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33 | namespace utility { |
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34 | class vector; |
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35 | } |
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36 | namespace statistics { |
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37 | |
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38 | /// |
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39 | /// Class for Fisher's t-test. |
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40 | /// |
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41 | /// See <a href="http://en.wikipedia.org/wiki/Student's_t-test"> |
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42 | /// http://en.wikipedia.org/wiki/Student's_t-test</a> for more |
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43 | /// details on the t-test. |
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44 | /// |
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45 | class tScore : public Score |
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46 | { |
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47 | |
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48 | public: |
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49 | /// |
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50 | /// Default Constructor. |
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51 | /// |
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52 | tScore(bool absolute=true); |
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53 | |
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54 | |
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55 | /** |
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56 | Calculates the value of t-score, i.e. the ratio between |
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57 | difference in mean and standard deviation of this |
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58 | difference. \f$ t = \frac{ m_x - m_y } |
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59 | {s\sqrt{\frac{1}{n_x}+\frac{1}{n_y}}} \f$ where \f$ m \f$ is the |
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60 | mean, \f$ n \f$ is the number of data points and \f$ s^2 = |
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61 | \frac{ \sum_i (x_i-m_x)^2 + \sum_i (y_i-m_y)^2 }{ n_x + n_y - |
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62 | 2 } \f$ |
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63 | |
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64 | @return t-score. If absolute=true absolute value of t-score |
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65 | is returned |
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66 | */ |
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67 | double score(const classifier::Target& target, |
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68 | const utility::vector& value); |
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69 | |
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70 | /** |
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71 | Calculates the weighted t-score, i.e. the ratio between |
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72 | difference in mean and standard deviation of this |
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73 | difference. \f$ t = \frac{ m_x - m_y }{ |
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74 | s\sqrt{\frac{1}{n_x}+\frac{1}{n_y}}} \f$ where \f$ m \f$ is the |
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75 | weighted mean, n is the weighted version of number of data |
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76 | points \f$ \frac{\left(\sum w_i\right)^2}{\sum w_i^2} \f$, and |
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77 | \f$ s^2 \f$ is an estimation of the variance \f$ s^2 = \frac{ |
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78 | \sum_i w_i(x_i-m_x)^2 + \sum_i w_i(y_i-m_y)^2 }{ n_x + n_y - 2 |
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79 | } \f$. See AveragerWeighted for details. |
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80 | |
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81 | @return t-score. If absolute=true absolute value of t-score |
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82 | is returned |
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83 | */ |
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84 | double score(const classifier::Target& target, |
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85 | const classifier::DataLookupWeighted1D& value); |
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86 | |
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87 | /// |
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88 | /// Calculates the weighted t-score, i.e. the ratio between |
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89 | /// difference in mean and standard deviation of this |
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90 | /// difference. \f$ t = \frac{ m_x - m_y }{ |
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91 | /// \frac{s2}{n_x}+\frac{s2}{n_y}} \f$ where \f$ m \f$ is the |
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92 | /// weighted mean, n is the weighted version of number of data |
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93 | /// points and \f$ s2 \f$ is an estimation of the variance \f$ s^2 |
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94 | /// = \frac{ \sum_i w_i(x_i-m_x)^2 + \sum_i w_i(y_i-m_y)^2 }{ n_x |
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95 | /// + n_y - 2 } \f$. See AveragerWeighted for details. |
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96 | /// |
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97 | /// @return t-score if absolute=true absolute value of t-score |
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98 | /// is returned |
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99 | /// |
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100 | double score(const classifier::Target& target, |
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101 | const utility::vector& value, |
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102 | const utility::vector& weight); |
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103 | |
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104 | /// |
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105 | /// Calculates the p-value, i.e. the probability of observing a |
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106 | /// t-score equally or larger if the null hypothesis is true. If P |
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107 | /// is near zero, this casts doubt on this hypothesis. The null |
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108 | /// hypothesis is that the means of the two distributions are |
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109 | /// equal. Assumtions for this test is that the two distributions |
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110 | /// are normal distributions with equal variance. The latter |
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111 | /// assumtion is dropped in Welch's t-test. |
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112 | /// |
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113 | /// @return the one-sided p-value( if absolute=true is used |
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114 | /// the two-sided p-value) |
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115 | /// |
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116 | double p_value() const; |
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117 | |
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118 | |
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119 | |
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120 | private: |
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121 | double t_; |
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122 | double dof_; |
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123 | |
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124 | }; |
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125 | |
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126 | }} // of namespace statistics and namespace theplu |
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127 | |
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128 | #endif |
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129 | |
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