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// $Id$ |
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/* |
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Copyright (C) 2004 Jari Häkkinen |
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Copyright (C) 2005 Peter Johansson |
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Copyright (C) 2006 Jari Häkkinen |
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This file is part of the thep c++ tools library, |
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http://lev.thep.lu.se/trac/c++_tools |
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The c++ tools library is free software; you can redistribute it |
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and/or modify it under the terms of the GNU General Public License |
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as published by the Free Software Foundation; either version 3 of |
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the License, or (at your option) any later version. |
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The c++ tools library is distributed in the hope that it will be |
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useful, but WITHOUT ANY WARRANTY; without even the implied warranty |
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of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with WeNNI. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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#include <c++_tools/utility/NNI.h> |
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#include <c++_tools/utility/stl_utility.h> |
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#include <algorithm> |
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#include <cmath> |
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#include <fstream> |
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namespace theplu { |
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namespace utility { |
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using namespace std; |
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// For a discussion and motivation for various algorithm |
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// implementations here see the paper cited in the class definition |
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// documentation. |
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NNI::NNI(const gslapi::matrix& matrix,const gslapi::matrix& weight, |
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const unsigned int neighbours) |
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: data_(matrix), imputed_data_(matrix), neighbours_(neighbours), |
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weight_(weight) |
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{ |
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} |
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// d_{ij}^2=\frac {\sum_{k=1,C} w_{ik} w_{jk} (x_{ik}-x_{jk})^2 } |
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// {\sum_{k=l,C} w_{ik} w_{jk} } |
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// where C is the number of columns |
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vector<pair<unsigned int,double> > NNI::calculate_distances(const unsigned int row) const |
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{ |
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vector<pair<unsigned int,double> > distance; |
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for (size_t i=0; i<data_.rows(); i++) |
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if (i!=row) { |
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double contribs=0; |
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pair<unsigned int,double> this_distance(i,0.0); |
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for (size_t j=0; j<data_.columns(); j++) |
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// 0 contribution for missing values |
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if (weight_(i,j) && weight_(row,j)) { |
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double weight_factor=weight_(i,j)*weight_(row,j); |
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this_distance.second+=( weight_factor * |
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(data_(i,j)-data_(row,j)) * |
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(data_(i,j)-data_(row,j)) ); |
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contribs+=weight_factor; |
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} |
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if (contribs) { // ignore lines without any contributions |
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this_distance.second=sqrt(this_distance.second/contribs); |
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distance.push_back(this_distance); |
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} |
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} |
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return distance; |
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} |
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// Contributing nearest neighbours are added up to the user set |
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// number, and neighbours are disqualified if their element (column) |
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// weight is zero |
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vector<unsigned int> |
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NNI::nearest_neighbours(const unsigned int column, |
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const vector<pair<unsigned int,double> >& d) const |
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{ |
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vector<unsigned int> index; |
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double contribs=0; |
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for (unsigned int i=0; ((i<d.size()) && |
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(contribs+=weight_(d[i].first,column))<=neighbours_); i++) |
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if (weight_(d[i].first,column)) |
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index.push_back(i); |
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return index; |
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} |
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}} // of namespace utility and namespace theplu |