1 | /*
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2 | * This program is free software; you can redistribute it and/or modify
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3 | * it under the terms of the GNU General Public License as published by
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4 | * the Free Software Foundation; either version 2 of the License, or
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5 | * (at your option) any later version.
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6 | *
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7 | * This program is distributed in the hope that it will be useful,
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8 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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9 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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10 | * GNU General Public License for more details.
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11 | *
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12 | * You should have received a copy of the GNU General Public License
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13 | * along with this program; if not, write to the Free Software
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14 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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15 | */
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16 |
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17 | /*
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18 | * Stats.java
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19 | * Copyright (C) 1999 Len Trigg
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20 | *
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21 | */
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22 |
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23 |
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24 | package weka.experiment;
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25 | import weka.core.Utils;
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26 |
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27 | /**
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28 | * A class to store simple statistics
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29 | *
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30 | * @author Len Trigg ([email protected])
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31 | * @version $Revision: 8815 $
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32 | */
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33 | public class Stats {
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34 |
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35 | /** The number of values seen */
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36 | public double count = 0;
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37 |
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38 | /** The sum of values seen */
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39 | public double sum = 0;
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40 |
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41 | /** The sum of values squared seen */
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42 | public double sumSq = 0;
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43 |
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44 | /** The std deviation of values at the last calculateDerived() call */
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45 | public double stdDev = Double.NaN;
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46 |
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47 | /** The mean of values at the last calculateDerived() call */
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48 | public double mean = Double.NaN;
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49 |
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50 | /** The minimum value seen, or Double.NaN if no values seen */
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51 | public double min = Double.NaN;
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52 |
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53 | /** The maximum value seen, or Double.NaN if no values seen */
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54 | public double max = Double.NaN;
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55 |
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56 | /**
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57 | * Adds a value to the observed values
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58 | *
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59 | * @param value the observed value
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60 | */
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61 | public void add(double value) {
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62 |
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63 | add(value, 1);
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64 | }
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65 |
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66 | /**
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67 | * Adds a value that has been seen n times to the observed values
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68 | *
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69 | * @param value the observed value
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70 | * @param n the number of times to add value
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71 | */
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72 | public void add(double value, double n) {
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73 |
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74 | sum += value * n;
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75 | sumSq += value * value * n;
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76 | count += n;
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77 | if (Double.isNaN(min)) {
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78 | min = max = value;
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79 | } else if (value < min) {
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80 | min = value;
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81 | } else if (value > max) {
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82 | max = value;
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83 | }
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84 | }
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85 |
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86 | /**
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87 | * Removes a value to the observed values (no checking is done
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88 | * that the value being removed was actually added).
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89 | *
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90 | * @param value the observed value
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91 | */
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92 | public void subtract(double value) {
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93 |
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94 | sum -= value;
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95 | sumSq -= value * value;
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96 | count --;
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97 | }
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98 |
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99 | /**
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100 | * Tells the object to calculate any statistics that don't have their
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101 | * values automatically updated during add. Currently updates the mean
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102 | * and standard deviation.
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103 | */
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104 | public void calculateDerived() {
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105 |
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106 | mean = Double.NaN;
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107 | stdDev = Double.NaN;
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108 | if (count > 0) {
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109 | mean = sum / count;
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110 | stdDev = Double.POSITIVE_INFINITY;
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111 | if (count > 1) {
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112 | stdDev = sumSq - (sum * sum) / count;
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113 | stdDev /= (count - 1);
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114 | if (stdDev < 0) {
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115 | System.err.println("Warning: stdDev value = " + stdDev
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116 | + " -- rounded to zero.");
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117 | stdDev = 0;
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118 | }
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119 | stdDev = Math.sqrt(stdDev);
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120 | }
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121 | }
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122 | }
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123 |
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124 | /**
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125 | * Returns a string summarising the stats so far.
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126 | *
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127 | * @return the summary string
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128 | */
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129 | public String toString() {
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130 |
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131 | calculateDerived();
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132 | return
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133 | "Count " + Utils.doubleToString(count, 8) + '\n'
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134 | + "Min " + Utils.doubleToString(min, 8) + '\n'
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135 | + "Max " + Utils.doubleToString(max, 8) + '\n'
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136 | + "Sum " + Utils.doubleToString(sum, 8) + '\n'
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137 | + "SumSq " + Utils.doubleToString(sumSq, 8) + '\n'
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138 | + "Mean " + Utils.doubleToString(mean, 8) + '\n'
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139 | + "StdDev " + Utils.doubleToString(stdDev, 8) + '\n';
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140 | }
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141 |
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142 | /**
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143 | * Tests the paired stats object from the command line.
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144 | * reads line from stdin, expecting two values per line.
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145 | *
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146 | * @param args ignored.
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147 | */
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148 | public static void main(String [] args) {
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149 |
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150 | try {
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151 | Stats ps = new Stats();
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152 | java.io.LineNumberReader r = new java.io.LineNumberReader(
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153 | new java.io.InputStreamReader(System.in));
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154 | String line;
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155 | while ((line = r.readLine()) != null) {
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156 | line = line.trim();
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157 | if (line.equals("") || line.startsWith("@") || line.startsWith("%")) {
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158 | continue;
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159 | }
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160 | java.util.StringTokenizer s
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161 | = new java.util.StringTokenizer(line, " ,\t\n\r\f");
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162 | int count = 0;
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163 | double v1 = 0;
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164 | while (s.hasMoreTokens()) {
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165 | double val = (new Double(s.nextToken())).doubleValue();
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166 | if (count == 0) {
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167 | v1 = val;
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168 | } else {
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169 | System.err.println("MSG: Too many values in line \""
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170 | + line + "\", skipped.");
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171 | break;
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172 | }
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173 | count++;
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174 | }
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175 | if (count == 1) {
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176 | ps.add(v1);
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177 | }
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178 | }
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179 | ps.calculateDerived();
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180 | System.err.println(ps);
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181 | } catch (Exception ex) {
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182 | ex.printStackTrace();
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183 | System.err.println(ex.getMessage());
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184 | }
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185 | }
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186 |
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187 | } // Stats
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188 |
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