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1 import java.applet.Applet  ;
2 import java.awt.BorderLayout ;
3 import java.awt.Button ;
4 import java.awt.Panel ;
5 import java.awt.event.ActionEvent ;
6 import java.awt.event.ActionListener ;
7 import java.util.Properties ;
8
9 import jcckit.Graphics2DPlotCanvas;
10 import jcckit.GraphicsPlotCanvas;
11 import jcckit.data.DataCurve;
12 import jcckit.data.DataPlot;
13 import jcckit.data.DataPoint;
14 import jcckit.util.ConfigParameters;
15 import jcckit.util.PropertiesBasedConfigData;
16
17
18
23 public class Lorenz extends Applet {
24 private double _b = 8.0 / 3;
25 private double _sigma = 10;
26 private double _r = 28;
27 private double _dt = 0.015;
28 private double[] _x = new double[3];
29 private double[] _xDot1 = new double[3];
30 private double[] _xDot2 = new double[3];
31 private double[][] _walk = new double[50][2];
32 private int _walkIndex;
33 private DataPlot _dataPlot;
34 private Thread _animationThread;
35
36 public void init() {
37 GraphicsPlotCanvas plotCanvas
38 = createPlotCanvas("true".equals(getParameter("graphics2D")));
39
40 _dataPlot = new DataPlot();
41 _dataPlot.addElement(new DataCurve("")); reset();
43 plotCanvas.connect(_dataPlot);
44
45 setLayout(new BorderLayout ());
46 add(plotCanvas.getGraphicsCanvas(), BorderLayout.CENTER);
47 add(createControlPanel(), BorderLayout.SOUTH);
48 }
49
50 private GraphicsPlotCanvas createPlotCanvas(boolean graphics2D) {
51 Properties props = new Properties ();
52 ConfigParameters config
53 = new ConfigParameters(new PropertiesBasedConfigData(props));
54 props.put("foreground", "0xffffff");
55 props.put("background", "0");
56 props.put("plot/legendVisible", "false");
57 props.put("plot/coordinateSystem/xAxis/minimum", "-20");
58 props.put("plot/coordinateSystem/xAxis/maximum", "20");
59 props.put("plot/coordinateSystem/xAxis/ticLabelFormat", "%d");
60 props.put("plot/coordinateSystem/yAxis/axisLabel", "z");
61 props.put("plot/coordinateSystem/yAxis/minimum", "0");
62 props.put("plot/coordinateSystem/yAxis/maximum", "50");
63 props.put("plot/coordinateSystem/yAxis/ticLabelFormat", "%d");
64 props.put("plot/curveFactory/definitions", "curve");
65 props.put("plot/curveFactory/curve/initialHintForNextPoint/className",
66 "jcckit.plot.ShapeAttributesHint");
67 props.put("plot/curveFactory/curve/initialHintForNextPoint/"
68 + "initialAttributes/fillColor", "0x50a");
69 props.put("plot/curveFactory/curve/initialHintForNextPoint/"
70 + "fillColorHSBIncrement", "0.0 0.0 0.018");
71 props.put("plot/curveFactory/curve/withLine", "false");
72 props.put("plot/curveFactory/curve/symbolFactory/className",
73 "jcckit.plot.CircleSymbolFactory");
74 props.put("plot/curveFactory/curve/symbolFactory/size", "0.015");
75
76 return graphics2D ? new Graphics2DPlotCanvas(config)
77 : new GraphicsPlotCanvas(config);
78 }
79
80 private Panel createControlPanel() {
81 Panel controlPanel = new Panel ();
82 Button startButton = new Button ("start");
83 startButton.addActionListener(new ActionListener () {
84 public void actionPerformed(ActionEvent e) {
85 _animationThread = new Thread () {
86 public void run() {
87 while (_animationThread != null) {
88 try {
89 Thread.sleep(50);
90 } catch (InterruptedException e) {}
91 next();
92 }
93 }
94 };
95 _animationThread.start();
96 }
97 });
98 controlPanel.add(startButton);
99 Button stopButton = new Button ("stop");
100 stopButton.addActionListener(new ActionListener () {
101 public void actionPerformed(ActionEvent e) {
102 _animationThread = null;
103 }
104 });
105 controlPanel.add(stopButton);
106 Button resetButton = new Button ("reset");
107 resetButton.addActionListener(new ActionListener () {
108 public void actionPerformed(ActionEvent e) {
109 reset();
110 }
111 });
112 controlPanel.add(resetButton);
113
114 return controlPanel;
115 }
116
117 private void reset() {
118 _x[0] = 10 * (Math.random() - 0.5);
119 _x[1] = 10 * (Math.random() - 0.5);
120 _x[2] = 10;
121 for (int i = 0; i < _walk.length; i++) {
122 _walk[i][0] = _x[0];
123 _walk[i][1] = _x[2];
124 }
125 updateCurve();
126 }
127
128 private void next() {
129 integrate();
130 _walk[_walkIndex][0] = _x[0];
131 _walk[_walkIndex][1] = _x[2];
132 _walkIndex = (_walkIndex + 1) % _walk.length;
133 updateCurve();
134 }
135
136
140 private void integrate() {
141 calculateDerivatives(_x, _xDot1);
142 for (int i = 0; i < _x.length; i++) {
143 _x[i] += _dt * _xDot1[i];
144 }
145 calculateDerivatives(_x, _xDot2);
146 for (int i = 0; i < _x.length; i++) {
147 _x[i] += 0.5 * _dt * (_xDot2[i] - _xDot1[i]);
148 }
149 }
150
151 private void calculateDerivatives(double[] x, double[] xDot) {
152 xDot[0] = _sigma * (x[1] - x[0]);
153 xDot[1] = _r * x[0] - x[1] - x[0] * x[2];
154 xDot[2] = x[0] * x[1] - _b * x[2];
155 }
156
157 private void updateCurve() {
158 DataCurve curve = new DataCurve("trajectory");
159 for (int i = 0; i < _walk.length; i++) {
160 int index = (_walkIndex + i) % _walk.length;
161 curve.addElement(new DataPoint(_walk[index][0], _walk[index][1]));
162 }
163 _dataPlot.replaceElementAt(0, curve);
164 }
165 }
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