sascha@357: package de.intevation.gnv.math;
sascha@357: 
sascha@357: import org.apache.commons.math.FunctionEvaluationException;
sascha@357: 
sascha@433: import org.apache.commons.math.analysis.UnivariateRealFunction;
sascha@433: 
sascha@779: import org.apache.commons.math.optimization.fitting.ParametricRealFunction;
sascha@779: 
sascha@357: /**
sascha@514:  *  @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
sascha@357:  */
sascha@357: public class LinearFunction
sascha@357: implements   ParametricRealFunction
sascha@357: {
sascha@357:     public static final LinearFunction INSTANCE = new LinearFunction();
sascha@357: 
sascha@778:     public static class Univariate
sascha@433:     implements          UnivariateRealFunction
sascha@433:     {
sascha@433:         protected double m;
sascha@433:         protected double b;
sascha@433: 
sascha@433:         public Univariate() {
sascha@433:         }
sascha@433: 
sascha@433:         public Univariate(double x1, double y1, double x2, double y2) {
sascha@433:             if (y1 == y2) {
sascha@433:                 m = 0d;
sascha@433:                 b = (x1 + x2)*0.5d;
sascha@433:             }
sascha@433:             else {
sascha@433:                 m = (x1 - x2)/(y1 - y2);
sascha@433:                 b = y1 - m*x1;
sascha@433:             }
sascha@433:         }
sascha@433: 
sascha@433:         public double value(double x) {
sascha@433:             return m*x + b;
sascha@433:         }
sascha@433:     } // class Univariate
sascha@433: 
sascha@357:     public LinearFunction() {
sascha@357:     }
sascha@357: 
sascha@357:     public double value(double x, double [] parameters)
sascha@778:     throws FunctionEvaluationException
sascha@357:     {
sascha@357:         return x*parameters[0] + parameters[1];
sascha@357:     }
sascha@357: 
sascha@778:     public double [] gradient(double x, double [] parameters)
sascha@778:     throws FunctionEvaluationException
sascha@357:     {
sascha@357:         return new double [] { x, 1f };
sascha@357:     }
sascha@357: }
sascha@514: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :