1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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4 | *
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5 | * This file is part of HeuristicLab.
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6 | *
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7 | * HeuristicLab is free software: you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation, either version 3 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * HeuristicLab is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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19 | */
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20 | #endregion
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21 |
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22 | using System;
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23 | using System.Linq;
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24 | using HeuristicLab.Common;
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25 |
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26 | namespace HeuristicLab.Analysis.AlgorithmBehavior.Analyzers {
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27 | public static class DistanceMatrixToPoints {
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28 | /*
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29 | * Calculates a matrix of n-dimensional points from the distance matrix dm as described in
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30 | * http://math.stackexchange.com/questions/156161/finding-the-coordinates-of-points-from-distance-matrix/423898#423898
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31 | * and
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32 | * http://stackoverflow.com/questions/10963054/finding-the-coordinates-of-points-from-distance-matrix/17177833#17177833
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33 | *
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34 | */
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35 | public static double[][] ConvertDistanceMatrixToPoints(double[][] dm) {
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36 | double[][] points = new double[dm.Length][];
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37 | double[,] m = new double[dm.Length, dm.Length];
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38 | double[] q = new double[dm.Length]; //eigenvalues
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39 | double[,] v = new double[dm.Length, dm.Length]; //eigenvectors
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40 |
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41 | for (int i = 0; i < dm.Length; i++) {
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42 | for (int j = 0; j < dm.Length; j++) {
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43 | m[i, j] = 0.5 * (Math.Pow(dm[0][j], 2) + Math.Pow(dm[i][0], 2) - Math.Pow(dm[i][j], 2));
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44 | }
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45 | }
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46 |
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47 | //QR decomposition to get the upper part for smatrixevd
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48 | double[] tau;
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49 | double[,] r;
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50 | alglib.rmatrixqr(ref m, dm.Length, dm.Length, out tau);
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51 | alglib.rmatrixqrunpackr(m, dm.Length, dm.Length, out r);
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52 |
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53 | bool res = alglib.smatrixevd(r, dm.Length, 1, true, out q, out v);
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54 | if (!res) throw new Exception("Eigenvalue computation did not converge!");
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55 |
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56 | int zeroCnt = q.Count(x => x.IsAlmost(0) || x < 0.0);
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57 | for (int i = 0; i < dm.Length; i++) {
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58 | points[i] = new double[dm.Length - zeroCnt];
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59 | }
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60 |
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61 | int pi = 0;
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62 | for (int i = 0; i < dm.Length; i++) {
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63 | if (!q[i].IsAlmost(0.0) && q[i] > 0.0) {
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64 | for (int j = 0; j < dm.Length; j++) {
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65 | points[j][pi] = Math.Sqrt(q[i]) * v[j, i];
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66 | }
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67 | pi++;
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68 | }
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69 | }
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70 |
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71 | return points;
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72 | }
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73 |
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74 | public static double[][] MetricMDS(double[][] dm) {
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75 | double[][] points = new double[dm.Length][];
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76 | double[,] a = new double[dm.Length, dm.Length];
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77 | double[,] b = new double[dm.Length, dm.Length];
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78 | double[] ai = new double[dm.Length];
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79 | double[] aj = new double[dm.Length];
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80 | double aavg = 0.0;
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81 | double[] q = new double[dm.Length];
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82 | double[,] v = new double[dm.Length, dm.Length];
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83 |
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84 |
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85 | for (int i = 0; i < dm.Length; i++) {
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86 | for (int j = 0; j < dm.Length; j++) {
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87 | a[i, j] = -0.5 * Math.Pow(dm[i][j], 2);
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88 | aavg += a[i, j];
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89 | }
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90 | }
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91 |
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92 | aavg /= dm.Length * dm.Length;
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93 |
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94 | for (int i = 0; i < dm.Length; i++) {
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95 | ai[i] = dm[i].Average();
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96 | }
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97 |
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98 | for (int i = 0; i < dm.Length; i++) {
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99 | for (int j = 0; j < dm.Length; j++) {
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100 | aj[i] += dm[j][i];
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101 | }
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102 | aj[i] /= dm.Length;
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103 | }
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104 |
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105 | for (int i = 0; i < dm.Length; i++) {
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106 | for (int j = 0; j < dm.Length; j++) {
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107 | b[i, j] = a[i, j] - ai[i] - aj[j] + aavg;
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108 | }
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109 | }
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110 |
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111 | //TODO: check b for negative values and make it positiv
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112 |
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113 | double[] tau;
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114 | double[,] r;
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115 | alglib.rmatrixqr(ref b, dm.Length, dm.Length, out tau);
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116 | alglib.rmatrixqrunpackr(b, dm.Length, dm.Length, out r);
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117 |
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118 | bool res = alglib.smatrixevd(r, dm.Length, 1, true, out q, out v);
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119 | if (!res) throw new Exception("Eigenvalue computation did not converge!");
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120 |
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121 | int zeroCnt = q.Count(x => x.IsAlmost(0) || x < 0.0);
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122 | for (int i = 0; i < dm.Length; i++) {
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123 | points[i] = new double[dm.Length - zeroCnt];
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124 | }
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125 |
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126 | int pi = 0;
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127 | for (int i = 0; i < dm.Length; i++) {
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128 | if (!q[i].IsAlmost(0.0) && q[i] > 0.0) {
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129 | for (int j = 0; j < dm.Length; j++) {
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130 | points[j][pi] = Math.Sqrt(q[i]) * v[j, i];
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131 | }
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132 | pi++;
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133 | }
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134 | }
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135 |
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136 | return points;
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137 | }
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138 | }
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139 | }
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