Mercurial > dive4elements > river

annotate artifacts/src/main/java/org/dive4elements/river/artifacts/math/Linear.java @ 5863:4897a58c8746

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River artifacts: Added new copyright headers.
author Sascha L. Teichmann <teichmann@intevation.de>
date Sun, 28 Apr 2013 14:40:59 +0200
parents 5aa05a7a34b7
children af13ceeba52a
rev   line source
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4897a58c8746 River artifacts: Added new copyright headers.
Sascha L. Teichmann <teichmann@intevation.de>
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1 /* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde
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2 * Software engineering by Intevation GmbH
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3 *
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4 * This file is Free Software under the GNU AGPL (>=v3)
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5 * and comes with ABSOLUTELY NO WARRANTY! Check out the
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6 * documentation coming with Dive4Elements River for details.
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7 */
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8
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9 package org.dive4elements.river.artifacts.math;
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10
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11 public final class Linear
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12 implements Function
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13 {
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14 private double m;
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15 private double b;
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16
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17 public Linear(
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18 double x1, double x2,
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19 double y1, double y2
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20 ) {
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21 // y1 = m*x1 + b
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22 // y2 = m*x2 + b
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23 // y2 - y1 = m*(x2 - x1)
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24 // m = (y2 - y1)/(x2 - x1) # x2 != x1
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25 // b = y1 - m*x1
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26
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27 if (x1 == x2) {
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28 m = 0;
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29 b = 0.5*(y1 + y2);
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30 }
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31 else {
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32 m = (y2 - y1)/(x2 - x1);
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33 b = y1 - m*x1;
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34 }
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35 }
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36
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37 public static final double linear(
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38 double x,
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39 double x1, double x2,
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40 double y1, double y2
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41 ) {
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42 // y1 = m*x1 + b
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43 // y2 = m*x2 + b
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44 // y2 - y1 = m*(x2 - x1)
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45 // m = (y2 - y1)/(x2 - x1) # x2 != x1
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46 // b = y1 - m*x1
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47
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48 if (x1 == x2) {
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49 return 0.5*(y1 + y2);
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50 }
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51 double m = (y2 - y1)/(x2 - x1);
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52 double b = y1 - m*x1;
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53 return x*m + b;
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54 }
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55
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56 @Override
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57 public double value(double x) {
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58 return m*x + b;
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59 }
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60
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61 public static final double factor(double x, double p1, double p2) {
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62 // 0 = m*p1 + b <=> b = -m*p1
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63 // 1 = m*p2 + b
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64 // 1 = m*(p2 - p1)
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65 // m = 1/(p2 - p1) # p1 != p2
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66 // f(x) = x/(p2-p1) - p1/(p2-p1) <=> (x-p1)/(p2-p1)
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67
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68 return p1 == p2 ? 0.0 : (x-p1)/(p2-p1);
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69 }
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70
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71 public static final double weight(double factor, double a, double b) {
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72 //return (1.0-factor)*a + factor*b;
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73 return a + factor*(b-a);
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74 }
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75
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76 public static final void weight(
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77 double factor,
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78 double [] a, double [] b, double [] c
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79 ) {
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80 int N = Math.min(Math.min(a.length, b.length), c.length);
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81 for (int i = 0; i < N; ++i) {
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82 c[i] = weight(factor, a[i], b[i]);
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83 }
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84 }
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85 }
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86 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :
http://dive4elements.wald.intevation.org