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> |
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date | Tue, 26 Jun 2012 06:33:37 +0000 |
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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 : |