Mercurial > dive4elements > river

annotate flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/Linear.java @ 2187:de5f391fdc8f

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Added strings used in the calculation 'historical discharge curves'. flys-artifacts/trunk@3797 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author Ingo Weinzierl <ingo.weinzierl@intevation.de>
date Fri, 27 Jan 2012 13:09:50 +0000
parents c09c9e05ecfa
children da1969b05292
rev   line source
655
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1 package de.intevation.flys.artifacts.math;
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2
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3 public final class Linear
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4 implements Function
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5 {
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6 private double m;
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7 private double b;
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8
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9 public Linear(
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10 double x1, double x2,
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11 double y1, double y2
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12 ) {
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13 // y1 = m*x1 + b
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14 // y2 = m*x2 + b
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15 // y2 - y1 = m*(x2 - x1)
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16 // m = (y2 - y1)/(x2 - x1) # x2 != x1
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17 // b = y1 - m*x1
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18
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19 if (x1 == x2) {
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20 m = 0;
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21 b = 0.5*(y1 + y2);
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22 }
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23 else {
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24 m = (y2 - y1)/(x2 - x1);
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25 b = y1 - m*x1;
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26 }
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27 }
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28
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29 public static final double linear(
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30 double x,
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31 double x1, double x2,
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32 double y1, double y2
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33 ) {
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34 // y1 = m*x1 + b
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35 // y2 = m*x2 + b
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36 // y2 - y1 = m*(x2 - x1)
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37 // m = (y2 - y1)/(x2 - x1) # x2 != x1
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38 // b = y1 - m*x1
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39
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40 if (x1 == x2) {
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41 return 0.5*(y1 + y2);
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42 }
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43 double m = (y2 - y1)/(x2 - x1);
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44 double b = y1 - m*x1;
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45 return x*m + b;
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46 }
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47
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48 @Override
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49 public double value(double x) {
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50 return m*x + b;
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51 }
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52
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53 public static final double factor(double x, double p1, double p2) {
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54 // 0 = m*p1 + b <=> b = -m*p1
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55 // 1 = m*p2 + b
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56 // 1 = m*(p2 - p1)
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57 // m = 1/(p2 - p1) # p1 != p2
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58 // f(x) = x/(p2-p1) - p1/(p2-p1) <=> (x-p1)/(p2-p1)
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59
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60 return p1 == p2 ? 0.0 : (x-p1)/(p2-p1);
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61 }
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62
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63 public static final double weight(double factor, double a, double b) {
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64 //return (1.0-factor)*a + factor*b;
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65 return a + factor*(b-a);
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66 }
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67 }
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68 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :
http://dive4elements.wald.intevation.org