1 | // $Id: BootstrapSampler.cc 1486 2008-09-09 21:17:19Z jari $ |
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2 | |
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3 | /* |
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4 | Copyright (C) 2007 Jari Häkkinen, Peter Johansson |
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5 | Copyright (C) 2008 Peter Johansson |
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6 | |
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7 | This file is part of the yat library, http://dev.thep.lu.se/yat |
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8 | |
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9 | The yat library is free software; you can redistribute it and/or |
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10 | modify it under the terms of the GNU General Public License as |
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11 | published by the Free Software Foundation; either version 3 of the |
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12 | License, or (at your option) any later version. |
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13 | |
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14 | The yat library is distributed in the hope that it will be useful, |
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15 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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17 | General Public License for more details. |
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18 | |
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19 | You should have received a copy of the GNU General Public License |
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20 | along with this program; if not, write to the Free Software |
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21 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA |
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22 | 02111-1307, USA. |
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23 | */ |
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24 | |
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25 | #include "BootstrapSampler.h" |
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26 | #include "Target.h" |
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27 | #include "yat/random/random.h" |
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28 | |
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29 | #include <cassert> |
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30 | |
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31 | namespace theplu { |
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32 | namespace yat { |
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33 | namespace classifier { |
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34 | |
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35 | BootstrapSampler::BootstrapSampler(const Target& target, size_t N) |
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36 | : Sampler(target, N) |
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37 | { |
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38 | assert(target.size()>1); |
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39 | build(target, N); |
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40 | } |
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41 | |
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42 | BootstrapSampler::~BootstrapSampler() |
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43 | { |
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44 | } |
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45 | |
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46 | void BootstrapSampler::build(const Target& target, size_t N) |
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47 | { |
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48 | // index[i] gives all indices that belong to class i |
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49 | std::vector<std::vector<size_t> > index(target.nof_classes()); |
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50 | |
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51 | for (size_t i = 0; i<target.size(); ++i) |
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52 | index[target(i)].push_back(i); |
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53 | |
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54 | random::DiscreteUniform rnd; |
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55 | |
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56 | for (size_t i = 0; i<N; ++i){ |
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57 | std::vector<size_t> training_index; |
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58 | std::vector<size_t> validation_index; |
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59 | training_index.reserve(target.size()); |
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60 | validation_index.reserve(target.size()); |
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61 | |
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62 | for (size_t label=0; label<target.nof_classes(); ++label) { |
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63 | std::vector<char> drawn(index[label].size(),0); |
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64 | for (size_t j=0; j<index[label].size(); ++j) { |
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65 | size_t k = rnd(index[label].size()); |
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66 | training_index.push_back(index[label][k]); |
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67 | drawn[k]=1; |
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68 | } |
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69 | for (size_t j=0; j<index[label].size(); ++j) |
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70 | if (!drawn[j]) { |
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71 | validation_index.push_back(index[label][j]); |
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72 | } |
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73 | } |
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74 | training_index_.push_back(utility::Index(training_index)); |
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75 | training_target_.push_back(Target(target,utility::Index(training_index))); |
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76 | validation_index_.push_back(utility::Index(validation_index)); |
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77 | validation_target_.push_back(Target(target, |
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78 | utility::Index(validation_index))); |
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79 | } |
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80 | |
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81 | } |
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82 | |
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83 | }}} // of namespace classifier, yat, and theplu |
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