Mercurial > dive4elements > river
diff flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvQuad.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/InvQuad.java Tue Jun 26 10:45:33 2012 +0000 +++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvQuad.java Tue Jun 26 10:54:12 2012 +0000 @@ -3,28 +3,62 @@ public class InvQuad extends Function { + public static final Derivative DERIVATIVE = + new Derivative("Q'(W) = 1/sqrt(4*n*(W-b)+m^2)") { + + @Override + public de.intevation.flys.artifacts.math.Function + instantiate(double [] parameters) + { + double n = parameters[0]; + double m = parameters[1]; + final double b = parameters[2]; + final double n4 = 4d*n; + final double mm = m*m; + + return new de.intevation.flys.artifacts.math.Function() { + @Override + public double value(double W) { + return 1d/Math.sqrt(n4*(W-b)+mm); + } + }; + } + }; + public static final Function INSTANCE = new InvQuad(); public InvQuad() { - // TODO: Implement me! + super( + "inv-quad", + "(sqrt(4*n*W-4*b*n+m^2)-m)/(2*n)", + new String [] { "n", "m", "b" }); } @Override public double value(double W, double [] parameters) { - // TODO: Implement me! - return 0d; + double n = parameters[0]; + double m = parameters[1]; + double b = parameters[2]; + return (Math.sqrt(4d*n*(W - b) + m*m)-m)/(2d*n); } @Override - public double [] gradient(double Q, double [] parameters) { - // TODO: Implement me! - return null; + public double [] gradient(double W, double [] parameters) { + double n = parameters[0]; + double m = parameters[1]; + double b = parameters[2]; + double Wb = W-b; + double sn4Wb = Math.sqrt(4d*n*Wb + m*m); + return new double [] { + Wb/(n*sn4Wb)-(sn4Wb-m)/(2d*n*n), + (m/sn4Wb-1d)/(2d*n), + -1d/sn4Wb + }; } @Override public Derivative getDerivative() { - // TODO: Implement me! - return null; + return DERIVATIVE; } @Override