Mercurial > dive4elements > gnv-client
comparison gnv-artifacts/src/main/java/de/intevation/gnv/math/LinearFunction.java @ 1119:7c4f81f74c47
merged gnv-artifacts
| author | Thomas Arendsen Hein <thomas@intevation.de> |
|---|---|
| date | Fri, 28 Sep 2012 12:14:00 +0200 |
| parents | f953c9a559d8 |
| children |
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| 1027:fca4b5eb8d2f | 1119:7c4f81f74c47 |
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| 1 /* | |
| 2 * Copyright (c) 2010 by Intevation GmbH | |
| 3 * | |
| 4 * This program is free software under the LGPL (>=v2.1) | |
| 5 * Read the file LGPL.txt coming with the software for details | |
| 6 * or visit http://www.gnu.org/licenses/ if it does not exist. | |
| 7 */ | |
| 8 | |
| 9 package de.intevation.gnv.math; | |
| 10 | |
| 11 import org.apache.commons.math.FunctionEvaluationException; | |
| 12 | |
| 13 import org.apache.commons.math.analysis.UnivariateRealFunction; | |
| 14 | |
| 15 import org.apache.commons.math.optimization.fitting.ParametricRealFunction; | |
| 16 | |
| 17 /** | |
| 18 * Models a linear function to be usable in the fitting framework of | |
| 19 * the Apache Commons Mathematics Library. | |
| 20 * | |
| 21 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> | |
| 22 */ | |
| 23 public class LinearFunction | |
| 24 implements ParametricRealFunction | |
| 25 { | |
| 26 /** | |
| 27 * Instance to prevent needless creations of instances. | |
| 28 */ | |
| 29 public static final LinearFunction INSTANCE = new LinearFunction(); | |
| 30 | |
| 31 /** | |
| 32 * Specialized class to be useful in function evaluating | |
| 33 * in the Apache Commons Mathematics Library. | |
| 34 */ | |
| 35 public static class Univariate | |
| 36 implements UnivariateRealFunction | |
| 37 { | |
| 38 /** | |
| 39 * The linear scaling factor. | |
| 40 */ | |
| 41 protected double m; | |
| 42 /** | |
| 43 * The linear offset. | |
| 44 */ | |
| 45 protected double b; | |
| 46 | |
| 47 /** | |
| 48 * Default constructor. | |
| 49 */ | |
| 50 public Univariate() { | |
| 51 } | |
| 52 | |
| 53 /** | |
| 54 * Constructor to create a Univariate with the linear parameters | |
| 55 * of the line between (x1, y1) and (x2, y2). | |
| 56 * @param x1 The x coordinate of the first point. | |
| 57 * @param y1 The y coordinate of the first point. | |
| 58 * @param x2 The x coordinate of the second point. | |
| 59 * @param y2 The y coordinate of the second point. | |
| 60 */ | |
| 61 public Univariate(double x1, double y1, double x2, double y2) { | |
| 62 if (y1 == y2) { | |
| 63 m = 0d; | |
| 64 b = (x1 + x2)*0.5d; | |
| 65 } | |
| 66 else { | |
| 67 m = (x1 - x2)/(y1 - y2); | |
| 68 b = y1 - m*x1; | |
| 69 } | |
| 70 } | |
| 71 | |
| 72 public double value(double x) { | |
| 73 return m*x + b; | |
| 74 } | |
| 75 } // class Univariate | |
| 76 | |
| 77 /** | |
| 78 * Default constructor. | |
| 79 */ | |
| 80 public LinearFunction() { | |
| 81 } | |
| 82 | |
| 83 public double value(double x, double [] parameters) | |
| 84 throws FunctionEvaluationException | |
| 85 { | |
| 86 return x*parameters[0] + parameters[1]; | |
| 87 } | |
| 88 | |
| 89 public double [] gradient(double x, double [] parameters) | |
| 90 throws FunctionEvaluationException | |
| 91 { | |
| 92 return new double [] { x, 1f }; | |
| 93 } | |
| 94 } | |
| 95 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |