1 | // $Id: NNI.cc 1275 2008-04-11 06:10:12Z jari $ |
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2 | |
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3 | /* |
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4 | Copyright (C) 2004 Jari Häkkinen |
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5 | Copyright (C) 2005 Peter Johansson |
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6 | Copyright (C) 2006 Jari Häkkinen |
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7 | Copyright (C) 2007 Jari Häkkinen, Peter Johansson |
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8 | Copyright (C) 2008 Peter Johansson |
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9 | |
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10 | This file is part of the yat library, http://trac.thep.lu.se/yat |
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11 | |
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12 | The yat library is free software; you can redistribute it and/or |
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13 | modify it under the terms of the GNU General Public License as |
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14 | published by the Free Software Foundation; either version 2 of the |
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15 | License, or (at your option) any later version. |
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16 | |
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17 | The yat library is distributed in the hope that it will be useful, |
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18 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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20 | General Public License for more details. |
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21 | |
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22 | You should have received a copy of the GNU General Public License |
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23 | along with this program; if not, write to the Free Software |
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24 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA |
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25 | 02111-1307, USA. |
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26 | */ |
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27 | |
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28 | #include "NNI.h" |
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29 | #include "stl_utility.h" |
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30 | |
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31 | #include <algorithm> |
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32 | #include <cmath> |
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33 | #include <fstream> |
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34 | |
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35 | namespace theplu { |
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36 | namespace yat { |
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37 | namespace utility { |
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38 | |
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39 | // For a discussion and motivation for various algorithm |
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40 | // implementations here see the paper cited in the class definition |
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41 | // documentation. |
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42 | NNI::NNI(const utility::Matrix& matrix,const utility::Matrix& weight, |
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43 | const unsigned int neighbours) |
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44 | : data_(matrix), imputed_data_(matrix), neighbours_(neighbours), |
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45 | weight_(weight) |
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46 | { |
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47 | } |
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48 | |
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49 | |
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50 | // d_{ij}^2=\frac {\sum_{k=1,C} w_{ik} w_{jk} (x_{ik}-x_{jk})^2 } |
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51 | // {\sum_{k=l,C} w_{ik} w_{jk} } |
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52 | // where C is the number of columns |
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53 | std::vector<std::pair<size_t,double> > |
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54 | NNI::calculate_distances(const size_t row) const |
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55 | { |
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56 | std::vector<std::pair<size_t,double> > distance; |
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57 | for (size_t i=0; i<data_.rows(); i++) |
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58 | if (i!=row) { |
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59 | double contribs=0; |
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60 | std::pair<size_t,double> this_distance(i,0.0); |
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61 | for (size_t j=0; j<data_.columns(); j++) |
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62 | // 0 contribution for missing values |
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63 | if (weight_(i,j) && weight_(row,j)) { |
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64 | double weight_factor=weight_(i,j)*weight_(row,j); |
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65 | this_distance.second+=( weight_factor * |
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66 | (data_(i,j)-data_(row,j)) * |
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67 | (data_(i,j)-data_(row,j)) ); |
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68 | contribs+=weight_factor; |
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69 | } |
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70 | if (contribs) { // ignore lines without any contributions |
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71 | this_distance.second=sqrt(this_distance.second/contribs); |
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72 | distance.push_back(this_distance); |
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73 | } |
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74 | } |
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75 | return distance; |
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76 | } |
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77 | |
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78 | |
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79 | const utility::Matrix& NNI::imputed_data(void) const |
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80 | { |
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81 | return imputed_data_; |
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82 | } |
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83 | |
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84 | |
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85 | const std::vector<size_t>& NNI::not_imputed(void) const |
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86 | { |
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87 | return not_imputed_; |
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88 | } |
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89 | |
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90 | |
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91 | // Contributing nearest neighbours are added up to the user set |
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92 | // number, and neighbours are disqualified if their element (column) |
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93 | // weight is zero |
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94 | std::vector<size_t> |
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95 | NNI::nearest_neighbours(const size_t column, |
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96 | const std::vector<std::pair<size_t,double> >& d) const |
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97 | { |
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98 | std::vector<size_t> index; |
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99 | double contribs=0; |
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100 | for (size_t i=0; ((i<d.size()) && |
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101 | (contribs+=weight_(d[i].first,column))<=neighbours_); i++) |
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102 | if (weight_(d[i].first,column)) |
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103 | index.push_back(i); |
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104 | return index; |
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105 | } |
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106 | |
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107 | }}} // of namespace utility, yat, and theplu |
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