Mercurial > dive4elements > gnv-client
view gnv-artifacts/src/main/java/de/intevation/gnv/math/LinearFunction.java @ 846:8b6ef091d38c
It is possible to draw VerticalProfileCharts with just one single data point (issue229).
gnv-artifacts/trunk@962 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author | Ingo Weinzierl <ingo.weinzierl@intevation.de> |
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date | Wed, 21 Apr 2010 08:46:23 +0000 |
parents | a645bd23c1c8 |
children | f953c9a559d8 |
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package de.intevation.gnv.math; import org.apache.commons.math.FunctionEvaluationException; import org.apache.commons.math.analysis.UnivariateRealFunction; import org.apache.commons.math.optimization.fitting.ParametricRealFunction; /** * Models a linear function to be usable in the fitting framework of * the Apache Commons Mathematics Library. * * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> */ public class LinearFunction implements ParametricRealFunction { /** * Instance to prevent needless creations of instances. */ public static final LinearFunction INSTANCE = new LinearFunction(); /** * Specialized class to be useful in function evaluating * in the Apache Commons Mathematics Library. */ public static class Univariate implements UnivariateRealFunction { /** * The linear scaling factor. */ protected double m; /** * The linear offset. */ protected double b; /** * Default constructor. */ public Univariate() { } /** * Constructor to create a Univariate with the linear parameters * of the line between (x1, y1) and (x2, y2). * @param x1 The x coordinate of the first point. * @param y1 The y coordinate of the first point. * @param x2 The x coordinate of the second point. * @param y2 The y coordinate of the second point. */ public Univariate(double x1, double y1, double x2, double y2) { if (y1 == y2) { m = 0d; b = (x1 + x2)*0.5d; } else { m = (x1 - x2)/(y1 - y2); b = y1 - m*x1; } } public double value(double x) { return m*x + b; } } // class Univariate /** * Default constructor. */ public LinearFunction() { } public double value(double x, double [] parameters) throws FunctionEvaluationException { return x*parameters[0] + parameters[1]; } public double [] gradient(double x, double [] parameters) throws FunctionEvaluationException { return new double [] { x, 1f }; } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :