Mercurial > dive4elements > gnv-client
comparison gnv-artifacts/src/main/java/de/intevation/gnv/math/LinearFunction.java @ 875:5e9efdda6894
merged gnv-artifacts/1.0
| author | Thomas Arendsen Hein <thomas@intevation.de> |
|---|---|
| date | Fri, 28 Sep 2012 12:13:56 +0200 |
| parents | a645bd23c1c8 |
| children | f953c9a559d8 |
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| 722:bb3ffe7d719e | 875:5e9efdda6894 |
|---|---|
| 1 package de.intevation.gnv.math; | |
| 2 | |
| 3 import org.apache.commons.math.FunctionEvaluationException; | |
| 4 | |
| 5 import org.apache.commons.math.analysis.UnivariateRealFunction; | |
| 6 | |
| 7 import org.apache.commons.math.optimization.fitting.ParametricRealFunction; | |
| 8 | |
| 9 /** | |
| 10 * Models a linear function to be usable in the fitting framework of | |
| 11 * the Apache Commons Mathematics Library. | |
| 12 * | |
| 13 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> | |
| 14 */ | |
| 15 public class LinearFunction | |
| 16 implements ParametricRealFunction | |
| 17 { | |
| 18 /** | |
| 19 * Instance to prevent needless creations of instances. | |
| 20 */ | |
| 21 public static final LinearFunction INSTANCE = new LinearFunction(); | |
| 22 | |
| 23 /** | |
| 24 * Specialized class to be useful in function evaluating | |
| 25 * in the Apache Commons Mathematics Library. | |
| 26 */ | |
| 27 public static class Univariate | |
| 28 implements UnivariateRealFunction | |
| 29 { | |
| 30 /** | |
| 31 * The linear scaling factor. | |
| 32 */ | |
| 33 protected double m; | |
| 34 /** | |
| 35 * The linear offset. | |
| 36 */ | |
| 37 protected double b; | |
| 38 | |
| 39 /** | |
| 40 * Default constructor. | |
| 41 */ | |
| 42 public Univariate() { | |
| 43 } | |
| 44 | |
| 45 /** | |
| 46 * Constructor to create a Univariate with the linear parameters | |
| 47 * of the line between (x1, y1) and (x2, y2). | |
| 48 * @param x1 The x coordinate of the first point. | |
| 49 * @param y1 The y coordinate of the first point. | |
| 50 * @param x2 The x coordinate of the second point. | |
| 51 * @param y2 The y coordinate of the second point. | |
| 52 */ | |
| 53 public Univariate(double x1, double y1, double x2, double y2) { | |
| 54 if (y1 == y2) { | |
| 55 m = 0d; | |
| 56 b = (x1 + x2)*0.5d; | |
| 57 } | |
| 58 else { | |
| 59 m = (x1 - x2)/(y1 - y2); | |
| 60 b = y1 - m*x1; | |
| 61 } | |
| 62 } | |
| 63 | |
| 64 public double value(double x) { | |
| 65 return m*x + b; | |
| 66 } | |
| 67 } // class Univariate | |
| 68 | |
| 69 /** | |
| 70 * Default constructor. | |
| 71 */ | |
| 72 public LinearFunction() { | |
| 73 } | |
| 74 | |
| 75 public double value(double x, double [] parameters) | |
| 76 throws FunctionEvaluationException | |
| 77 { | |
| 78 return x*parameters[0] + parameters[1]; | |
| 79 } | |
| 80 | |
| 81 public double [] gradient(double x, double [] parameters) | |
| 82 throws FunctionEvaluationException | |
| 83 { | |
| 84 return new double [] { x, 1f }; | |
| 85 } | |
| 86 } | |
| 87 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |