Mercurial > dive4elements > river
diff flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvPow.java @ 3181:de67497de5a0
Completed inverse functions.
flys-artifacts/trunk@4796 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author | Sascha L. Teichmann <sascha.teichmann@intevation.de> |
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date | Tue, 26 Jun 2012 10:54:12 +0000 |
parents | 59b14bc676ec |
children |
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--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvPow.java Tue Jun 26 10:45:33 2012 +0000 +++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvPow.java Tue Jun 26 10:54:12 2012 +0000 @@ -3,22 +3,59 @@ public class InvPow extends Function { + public static final Derivative DERIVATIVE = + new Derivative("Q'(W) = ((W-d)/a)^(1/c)/(c*(W-d))") { + + @Override + public de.intevation.flys.artifacts.math.Function + instantiate(double [] parameters) + { + double a = parameters[0]; + final double c = parameters[1]; + final double d = parameters[2]; + final double _1a = 1d/a; + final double _1c = 1d/c; + + return new de.intevation.flys.artifacts.math.Function() { + @Override + public double value(double W) { + double Wd = W-d; + return Math.pow(Wd*_1a, _1c)/(c*Wd); + } + }; + } + }; + public static final Function INSTANCE = new InvPow(); public InvPow() { - // TODO: Implement me! + super( + "pow", + "Q(W) = ((W-d)/a)^(1/c)", + new String [] { "a", "c", "d" }); } @Override public double value(double W, double [] parameters) { - // TODO: Implement me! - return 0d; + double a = parameters[0]; + double c = parameters[1]; + double d = parameters[2]; + return Math.pow((W-d)/a, 1d/c); } @Override - public double [] gradient(double Q, double [] parameters) { - // TODO: Implement me! - return null; + public double [] gradient(double W, double [] parameters) { + double a = parameters[0]; + double c = parameters[1]; + double d = parameters[2]; + double _1c = 1d/c; + double Wdac = Math.pow((W-d)/a, 1d/c); + double Wd = W-d; + return new double [] { + -Wdac/(a*c), + (Wdac*Math.log(Wd/a))/(c*c), + -Wdac/(c*Wd) + }; } @Override