Mercurial > dive4elements > river
comparison flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvExp.java @ 3177:585c0b49e696
Added inverses of the fitting functions.
flys-artifacts/trunk@4792 c6561f87-3c4e-4783-a992-168aeb5c3f6f
| author | Sascha L. Teichmann <sascha.teichmann@intevation.de> |
|---|---|
| date | Tue, 26 Jun 2012 06:33:37 +0000 |
| parents | |
| children |
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| 3176:cbaa49896eca | 3177:585c0b49e696 |
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| 1 package de.intevation.flys.artifacts.math.fitting; | |
| 2 | |
| 3 public class InvExp | |
| 4 extends Function | |
| 5 { | |
| 6 public static final Derivative DERIVATIVE = | |
| 7 new Derivative("W'(Q) = 1/(log(a)*(Q-b))") { | |
| 8 | |
| 9 @Override | |
| 10 public de.intevation.flys.artifacts.math.Function | |
| 11 instantiate(double [] parameters) | |
| 12 { | |
| 13 final double a = parameters[1]; | |
| 14 final double b = parameters[2]; | |
| 15 final double loga = Math.log(a); | |
| 16 | |
| 17 return new de.intevation.flys.artifacts.math.Function() { | |
| 18 @Override | |
| 19 public double value(double Q) { | |
| 20 return 1d/(loga*(Q-a)); | |
| 21 } | |
| 22 }; | |
| 23 } | |
| 24 }; | |
| 25 | |
| 26 public static final Function INSTANCE = new InvExp(); | |
| 27 | |
| 28 public InvExp() { | |
| 29 super( | |
| 30 "inv-exp", | |
| 31 "Q(W) = log((W-b)/m)/log(a)", | |
| 32 new String [] { "m", "a", "b" }); | |
| 33 } | |
| 34 | |
| 35 @Override | |
| 36 public double value(double W, double [] parameters) { | |
| 37 double m = parameters[0]; | |
| 38 double a = parameters[1]; | |
| 39 double b = parameters[2]; | |
| 40 return Math.log((W-b)/m)/Math.log(a); | |
| 41 } | |
| 42 | |
| 43 @Override | |
| 44 public double [] gradient(double Q, double [] parameters) { | |
| 45 double m = parameters[0]; | |
| 46 double a = parameters[1]; | |
| 47 double b = parameters[2]; | |
| 48 double loga = Math.log(a); | |
| 49 return new double [] { | |
| 50 -1d/(loga*m), | |
| 51 -Math.log((Q-b)/m)/(a*loga*loga), | |
| 52 -1d/(loga*(Q-b)) | |
| 53 }; | |
| 54 } | |
| 55 | |
| 56 @Override | |
| 57 public Derivative getDerivative() { | |
| 58 return DERIVATIVE; | |
| 59 } | |
| 60 | |
| 61 @Override | |
| 62 public Function getInverse() { | |
| 63 return Exp.INSTANCE; | |
| 64 } | |
| 65 } | |
| 66 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |