1 | using System;
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2 | using System.Collections.Generic;
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3 | using System.Linq;
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4 | using System.Text;
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5 | using System.Threading.Tasks;
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6 |
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7 | namespace HeuristicLab.Common {
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8 | public static class Extensions {
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9 | public static bool IsAlmost(this double x, double y) {
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10 | return Math.Abs(x - y) < 1.0e-12;
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11 | }
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12 |
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13 | public static T SelectRandom<T>(this IEnumerable<T> xs, Random rand) {
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14 | var xsArr = xs.ToArray();
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15 | return xsArr[rand.Next(xsArr.Length)];
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16 | }
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17 |
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18 | public static IEnumerable<T> SampleProportional<T>(this IEnumerable<T> source, Random random, IEnumerable<double> weights) {
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19 | var sourceArray = source.ToArray();
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20 | var valueArray = weights.ToArray();
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21 | double total = valueArray.Sum();
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22 |
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23 | while (true) {
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24 | int index = 0;
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25 | double ball = valueArray[index], sum = random.NextDouble() * total;
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26 | while (ball < sum)
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27 | ball += valueArray[++index];
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28 | yield return sourceArray[index];
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29 | }
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30 | }
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31 |
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32 | public static double RSq(IEnumerable<double> xs, IEnumerable<double> ys) {
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33 | // two pass implementation, but we don't care
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34 | var meanX = xs.Average();
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35 | var meanY = ys.Average();
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36 |
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37 | var s = 0.0;
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38 | var ssX = 0.0;
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39 | var ssY = 0.0;
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40 | var xEnum = xs.GetEnumerator();
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41 | var yEnum = ys.GetEnumerator();
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42 | while (xEnum.MoveNext() & yEnum.MoveNext()) {
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43 | var x = xEnum.Current;
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44 | var y = yEnum.Current;
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45 | s += (x - meanX) * (y - meanY);
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46 | ssX += Math.Pow(x - meanX, 2);
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47 | ssY += Math.Pow(y - meanY, 2);
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48 | }
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49 | if (xEnum.MoveNext() | yEnum.MoveNext()) throw new ArgumentException("lengths are not equal");
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50 |
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51 | if (s.IsAlmost(0)) return 0;
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52 | if (ssX.IsAlmost(0) || ssY.IsAlmost(0)) return 0;
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53 | return s * s / (ssX * ssY);
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54 | }
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55 |
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56 |
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57 | }
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58 | }
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