Mercurial > dive4elements > river
diff 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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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvExp.java Tue Jun 26 06:33:37 2012 +0000 @@ -0,0 +1,66 @@ +package de.intevation.flys.artifacts.math.fitting; + +public class InvExp +extends Function +{ + public static final Derivative DERIVATIVE = + new Derivative("W'(Q) = 1/(log(a)*(Q-b))") { + + @Override + public de.intevation.flys.artifacts.math.Function + instantiate(double [] parameters) + { + final double a = parameters[1]; + final double b = parameters[2]; + final double loga = Math.log(a); + + return new de.intevation.flys.artifacts.math.Function() { + @Override + public double value(double Q) { + return 1d/(loga*(Q-a)); + } + }; + } + }; + + public static final Function INSTANCE = new InvExp(); + + public InvExp() { + super( + "inv-exp", + "Q(W) = log((W-b)/m)/log(a)", + new String [] { "m", "a", "b" }); + } + + @Override + public double value(double W, double [] parameters) { + double m = parameters[0]; + double a = parameters[1]; + double b = parameters[2]; + return Math.log((W-b)/m)/Math.log(a); + } + + @Override + public double [] gradient(double Q, double [] parameters) { + double m = parameters[0]; + double a = parameters[1]; + double b = parameters[2]; + double loga = Math.log(a); + return new double [] { + -1d/(loga*m), + -Math.log((Q-b)/m)/(a*loga*loga), + -1d/(loga*(Q-b)) + }; + } + + @Override + public Derivative getDerivative() { + return DERIVATIVE; + } + + @Override + public Function getInverse() { + return Exp.INSTANCE; + } +} +// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :