Mercurial > dive4elements > gnv-client

comparison gnv-artifacts/src/main/java/de/intevation/gnv/math/XYColumn.java @ 1119:7c4f81f74c47

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merged gnv-artifacts
author Thomas Arendsen Hein <thomas@intevation.de>
date Fri, 28 Sep 2012 12:14:00 +0200
parents f953c9a559d8
children
comparison
equal deleted inserted replaced
1027:fca4b5eb8d2f 1119:7c4f81f74c47
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 java.util.ArrayList;
12 import java.util.Collections;
13 import java.util.List;
14
15 import org.apache.commons.math.FunctionEvaluationException;
16 import org.apache.commons.math.MathException;
17
18 import org.apache.commons.math.analysis.UnivariateRealFunction;
19
20 import org.apache.commons.math.analysis.interpolation.SplineInterpolator;
21 import org.apache.commons.math.analysis.interpolation.UnivariateRealInterpolator;
22
23 import org.apache.log4j.Logger;
24
25 /**
26 * A column of discrete attributed height values located at a point.
27 * Values between the discrete height values are interpolated.
28 *
29 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
30 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
31 */
32 public class XYColumn
33 extends Point2d
34 implements UnivariateRealFunction
35 {
36 private static Logger log = Logger.getLogger(XYColumn.class);
37
38 /**
39 * The list of discrete height values.
40 */
41 protected List<HeightValue> values;
42
43 /**
44 * The curve used to interpolate the points between the
45 * discrete height values.
46 */
47 protected transient UnivariateRealFunction curve;
48
49 /**
50 * Default constructor.
51 */
52 public XYColumn() {
53 values = new ArrayList<HeightValue>();
54 }
55
56 /**
57 * Constructor to create an XYColumn with a given (x, y) coordinate
58 * and an (i, j) index tuple.
59 * @param x The x coordinate.
60 * @param y The y coordinate.
61 * @param i The i component.
62 * @param j The j component.
63 */
64 public XYColumn(double x, double y, int i, int j) {
65 super(x, y, i, j);
66 values = new ArrayList<HeightValue>();
67 }
68
69 /**
70 * Adds a given height value to the list of height values.
71 * @param value The height value.
72 */
73 public void add(HeightValue value) {
74 values.add(value);
75 }
76
77 /**
78 * Returns the list of height values.
79 * @return The list of height values.
80 */
81 public List<HeightValue> getValues() {
82 return values;
83 }
84
85 public double value(double depth) {
86 try {
87 if (curve != null) {
88 HeightValue h = values.get(0);
89 // extrapolate beyond boundaries by repeating
90 if (depth > h.z) return h.v;
91 h = values.get(values.size()-1);
92 if (depth < h.z) return h.v;
93 return curve.value(depth);
94 }
95 }
96 catch (FunctionEvaluationException fee) {
97 log.error("evaluation failed", fee);
98 }
99
100 return Double.NaN;
101 }
102
103 /**
104 * Prepares this XYColumn to be queried. A given XYDepth
105 * object is used to fill the values to a certain depth.
106 * @param xyDepth To figure out the depth a the cordinate.
107 * @return true if preparation succeeds else false.
108 */
109 public boolean prepare(XYDepth xyDepth) {
110 if (curve == null) {
111 int N = values.size();
112 if (N == 0) {
113 log.error("no points for interpolation");
114 return false;
115 }
116
117 if (N == 1) {
118 // only one value -> constant function
119 curve = new ConstantFunction(values.get(0).v);
120 }
121 else { // more than on value
122 double depth = xyDepth.depth(this);
123 Collections.sort(values, HeightValue.INV_Z_COMPARATOR);
124
125 // if there is no value at 0 repeat first value
126 HeightValue first = values.get(0);
127 if (first.z < 0d) {
128 values.add(0, new HeightValue(0d, first.v, first.k-1));
129 ++N;
130 }
131
132 // if there is no value at depth repeat last value
133 HeightValue last = values.get(N-1);
134 if (last.z > depth) {
135 values.add(new HeightValue(depth, last.v, last.k+1));
136 ++N;
137 }
138 if (N < 3) { // interpolate linear
139 first = values.get(0);
140 last = values.get(N-1);
141 curve = new LinearFunction.Univariate(
142 first.z, first.v,
143 last.z, last.v);
144 }
145 else { // higher degree interpolation
146 double [] z = new double[N];
147 double [] v = new double[N];
148 for (int i = 0; i < N; ++i) {
149 HeightValue h = values.get(N-1-i);
150 z[i] = h.z;
151 v[i] = h.v;
152 }
153 try {
154 curve = getInterpolator().interpolate(z, v);
155 }
156 catch (MathException me) {
157 log.error("interpolation failed", me);
158 return false;
159 }
160 }
161 }
162 }
163 return true;
164 }
165
166 /**
167 * Returns the interpolator used to interpolate the values between
168 * the discrete height values. This class returns an instance of
169 * {@link org.apache.commons.math.analysis.interpolation.SplineInterpolator}.
170 * Override this if you want to use another kind of interpolation.
171 * @return The interpolator to be used.
172 */
173 protected UnivariateRealInterpolator getInterpolator() {
174 return new SplineInterpolator();
175 }
176 }
177 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :
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