Mercurial > dive4elements > river
comparison flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvLog.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 | 9422b559b2d5 |
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| 3176:cbaa49896eca | 3177:585c0b49e696 |
|---|---|
| 1 package de.intevation.flys.artifacts.math.fitting; | |
| 2 | |
| 3 public class InvLog | |
| 4 extends Function | |
| 5 { | |
| 6 public static final Derivative DERIVATIVE = | |
| 7 new Derivative("Q'(W) = exp(W/m)/m") { | |
| 8 | |
| 9 @Override | |
| 10 public de.intevation.flys.artifacts.math.Function | |
| 11 instantiate(double [] parameters) | |
| 12 { | |
| 13 final double _1m = 1d / parameters[0]; | |
| 14 | |
| 15 return new de.intevation.flys.artifacts.math.Function() { | |
| 16 @Override | |
| 17 public double value(double W) { | |
| 18 return Math.exp(W*_1m)*_1m; | |
| 19 } | |
| 20 }; | |
| 21 } | |
| 22 }; | |
| 23 | |
| 24 public static final Function INSTANCE = new InvLog(); | |
| 25 | |
| 26 public InvLog() { | |
| 27 super("inv-log", "Q(W) = e^(W/m) - b", new String [] { "m", "b" }); | |
| 28 } | |
| 29 | |
| 30 @Override | |
| 31 public double value(double w, double [] parameters) { | |
| 32 double m = parameters[0]; | |
| 33 double b = parameters[1]; | |
| 34 return Math.exp(w/m) - b; | |
| 35 } | |
| 36 | |
| 37 @Override | |
| 38 public double [] gradient(double w, double [] parameters) { | |
| 39 double m = parameters[0]; | |
| 40 double b = parameters[1]; | |
| 41 double ewm = Math.exp(w/m); | |
| 42 return new double [] { -w*ewm/(m*m), -1 }; | |
| 43 } | |
| 44 | |
| 45 @Override | |
| 46 public Derivative getDerivative() { | |
| 47 return DERIVATIVE; | |
| 48 } | |
| 49 | |
| 50 @Override | |
| 51 public Function getInverse() { | |
| 52 return Log.INSTANCE; | |
| 53 } | |
| 54 } | |
| 55 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : | |
| 56 |