[11659] | 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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[11727] | 7 | namespace HeuristicLab.Common {
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[11659] | 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-6;
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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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[11730] | 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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[11732] | 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 | foreach (var p in xs.Zip(ys, (x, y) => new { x, y })) {
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| 41 | s += (p.x - meanX) * (p.y - meanY);
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| 42 | ssX += Math.Pow(p.x - meanX, 2);
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| 43 | ssY += Math.Pow(p.y - meanY, 2);
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| 44 | }
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| 45 |
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| 46 | if (s.IsAlmost(0)) return 0;
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| 47 | if (ssX.IsAlmost(0) || ssY.IsAlmost(0)) return 0;
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| 48 | return s * s / (ssX * ssY);
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| 49 | }
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| 50 |
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| 51 |
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[11659] | 52 | }
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| 53 | }
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