Mercurial > dive4elements > river
comparison flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/Linear.java @ 3318:dbe2f85bf160
merged flys-artifacts/2.8
| author | Thomas Arendsen Hein <thomas@intevation.de> |
|---|---|
| date | Fri, 28 Sep 2012 12:14:35 +0200 |
| parents | c09c9e05ecfa |
| children | da1969b05292 |
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| 2987:98c7a46ec5ae | 3318:dbe2f85bf160 |
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| 1 package de.intevation.flys.artifacts.math; | |
| 2 | |
| 3 public final class Linear | |
| 4 implements Function | |
| 5 { | |
| 6 private double m; | |
| 7 private double b; | |
| 8 | |
| 9 public Linear( | |
| 10 double x1, double x2, | |
| 11 double y1, double y2 | |
| 12 ) { | |
| 13 // y1 = m*x1 + b | |
| 14 // y2 = m*x2 + b | |
| 15 // y2 - y1 = m*(x2 - x1) | |
| 16 // m = (y2 - y1)/(x2 - x1) # x2 != x1 | |
| 17 // b = y1 - m*x1 | |
| 18 | |
| 19 if (x1 == x2) { | |
| 20 m = 0; | |
| 21 b = 0.5*(y1 + y2); | |
| 22 } | |
| 23 else { | |
| 24 m = (y2 - y1)/(x2 - x1); | |
| 25 b = y1 - m*x1; | |
| 26 } | |
| 27 } | |
| 28 | |
| 29 public static final double linear( | |
| 30 double x, | |
| 31 double x1, double x2, | |
| 32 double y1, double y2 | |
| 33 ) { | |
| 34 // y1 = m*x1 + b | |
| 35 // y2 = m*x2 + b | |
| 36 // y2 - y1 = m*(x2 - x1) | |
| 37 // m = (y2 - y1)/(x2 - x1) # x2 != x1 | |
| 38 // b = y1 - m*x1 | |
| 39 | |
| 40 if (x1 == x2) { | |
| 41 return 0.5*(y1 + y2); | |
| 42 } | |
| 43 double m = (y2 - y1)/(x2 - x1); | |
| 44 double b = y1 - m*x1; | |
| 45 return x*m + b; | |
| 46 } | |
| 47 | |
| 48 @Override | |
| 49 public double value(double x) { | |
| 50 return m*x + b; | |
| 51 } | |
| 52 | |
| 53 public static final double factor(double x, double p1, double p2) { | |
| 54 // 0 = m*p1 + b <=> b = -m*p1 | |
| 55 // 1 = m*p2 + b | |
| 56 // 1 = m*(p2 - p1) | |
| 57 // m = 1/(p2 - p1) # p1 != p2 | |
| 58 // f(x) = x/(p2-p1) - p1/(p2-p1) <=> (x-p1)/(p2-p1) | |
| 59 | |
| 60 return p1 == p2 ? 0.0 : (x-p1)/(p2-p1); | |
| 61 } | |
| 62 | |
| 63 public static final double weight(double factor, double a, double b) { | |
| 64 //return (1.0-factor)*a + factor*b; | |
| 65 return a + factor*(b-a); | |
| 66 } | |
| 67 } | |
| 68 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |