I've done a class that converts the datasets to datasets following bezier lines between the given points. It's like the method used in PEAR Image_Graph in PHP.
The class is the following:
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import java.awt.geom.*;
import org.jfree.data.xy.*;
import org.jfree.data.time.*;
import java.util.*;
/**
* Creates smooth curves from different datasets, interpolating
* points following Bezier curves
*
* @author Roger Veciana
* @version 0.1, 03/21/07
*/
public class SmoothLine {
/** Total number of samples that the class will return with the dataset. */
private int samples = 100;
/** The smooth factor determinates how open are the bezier curves, and also how much do they fit to the data. */
private double smooth_factor = 0.75;
/** The points given by the user to be smoothed*/
private Point2D[] points;
/**
* Constructor from a Point2D array.
* @param points The Point2D array that will be used to get the reference points for the smooth line.
*/
public SmoothLine(Point2D[] points){
this.points = points;
}
public SmoothLine(TimeSeries time_serie){
//First, we set the Points2D array used to store the data
points = new Point2D[time_serie.getItemCount()];
//Fill the array
for(int i = 0; i < time_serie.getItemCount(); i++){
points[i] = new Point2D.Double(new Double(time_serie.getTimePeriod(i).getFirstMillisecond()), time_serie.getValue(i).doubleValue());
}
}
/**
* Gets and returns a Point2D array with int samples that can be used to
* fill a serie, or whatever.
* @param points the array of points to interpolate the Bezier lines.
* @param samples number of sampels to return.
*
* */
public Point2D[] getPoint2DArray() {
double x1=0;
double y1=0;
double x2=0;
double y2=0;
double x0;
double y0;
double x3;
double y3;
int samples_interval = Math.round(samples / (points.length-1));
Point2D[] points_return = new Point2D[samples];
int pos_return = 0; //we'll store the pointer in the points_return array here.
//We iterate between the different given points,
//calculating the Bezier curves between them
for(int i=0; i < points.length-1; i++){
//the last period may have a different number of samples in order to fit the sample value
if(i == points.length-2){
samples_interval = samples - (samples_interval*(points.length-2));
}
x1=points[i].getX();
x2=points[i+1].getX();
y1=points[i].getY();
y2=points[i+1].getY();
if(i>0){
x0=points[i-1].getX();
y0=points[i-1].getY();
}else {
x0 = x1 - Math.abs(x2 - x1);
y0 = y1;
}
if(i < points.length -2){
x3=points[i+2].getX();
y3=points[i+2].getY();
} else {
x3 = x1 + 2*Math.abs(x1 - x0);
y3 = y1;
}
Point2D[] points_bezier = CalculateBezierCurve(x0,y0,x1,y1,x2,y2,x3,y3, samples_interval);
//Fill the return array
for(int j = 0 ; j < points_bezier.length; j++){
points_return[pos_return] = new Point2D.Double(points_bezier[j].getX(),points_bezier[j].getY());
pos_return++;
}
}
return points_return;
}
/**
* Takes the points, calculates the Bezier curves and creates a XYSeries.
* @param serie_name The name of the serie that will appear in the Legend, for example.
* @return the XYSerie ready to be used.
* */
public XYSeries getXYSeries(String serie_name){
XYSeries serie = new XYSeries(serie_name);
Point2D[] points_bezier = getPoint2DArray();
for(int j = 0 ; j < points_bezier.length; j++){
serie.add(points_bezier[j].getX(),points_bezier[j].getY());
}
return serie;
}
/**
* Takes the points stored and creates a TimeSeries with a smooth line. If the contructor is not the one with TimeSeries as the parameter, the x value has to be UnixTimestamp in milliseconds.
* @param serie_name
* @return a TimeSeries with the name given as parameter and a Second.class as the RegularTimePeriod, to be able to interpolate.
*/
public TimeSeries getTimeSeries(String serie_name){
//First, we create the TimeSeries to return
TimeSeries time_serie= new TimeSeries(serie_name,Second.class);
//Gets the Bezier curves
Point2D[] points_bezier = getPoint2DArray();
for(int j = 0 ; j < points_bezier.length; j++){
//System.out.println(j + " X --> " + points_bezier[j].getX());
//time_serie.add(RegularTimePeriod.createInstance(Second.class,new Date((long)points_bezier[j].getX()),RegularTimePeriod.DEFAULT_TIME_ZONE),points_bezier[j].getY());
time_serie.add(new Second(new Date((long)points_bezier[j].getX())),points_bezier[j].getY());
}
return time_serie;
}
/**
* Calculates the Bezier curve between two points
* The idea is taken from the PEAR Image_Graph Smoothline
*
*
* @param x0 the point "just before" (<code>null</code> permitted).
* @param y0 the point "just before" (<code>null</code> permitted).
* @param x1 the actual point to calculate the control points for (<code>null</code> NOT permitted).
* @param y1 the actual point to calculate the control points for (<code>null</code> NOT permitted).
* @param x2 the point "just after" (<code>null</code> NOT permitted).
* @param y2 the point "just after" (<code>null</code> NOT permitted).
* @param x3 the point "just after" x2 (<code>null</code> permitted).
* @param y4 the point "just after" y2 (<code>null</code> permitted).
* @param samples_interval number of points generated between the given points
* */
private Point2D[] CalculateBezierCurve(double x0, double y0, double x1, double y1, double x2, double y2, double x3, double y3, int samples_interval){
double control_point_1_x;
double control_point_1_y;
double control_point_2_x;
double control_point_2_y;
//Calculate the control points for the cubic bezier line
control_point_1_x =controlPoint(x0,x1,x2);
control_point_1_y =controlPoint(y0,y1,y2);
control_point_2_x = controlPoint(x3,x2,x1);
control_point_2_y = controlPoint(y3,y2,y1);
//System.out.println("control1: " + control_point_1_x + " -- " + control_point_1_y);
//System.out.println("control2: " + control_point_2_x + " -- " + control_point_2_y);
double cx = 3.0 * (control_point_1_x - x1);
double bx = 3.0 * (control_point_2_x - control_point_1_x) - cx;
double ax = x2 - x1 - cx - bx;
double cy = 3.0 * (control_point_1_y - y1);
double by = 3.0 * (control_point_2_y - control_point_1_y) - cy;
double ay = y2 - y1 - cy - by;
//Let's calculate all the ponits that follow the Bezier curve.
Point2D[] points = new Point2D[samples_interval];
for(int j = 0; j < samples_interval; j++){
double t = j*(1.0/samples_interval);
//System.out.println("j: " + j + " t: " + t + " samples_int: " + (samples_interval));
double x = (ax * t * t * t) + (bx * t * t) + (cx * t) + x1;
double y = (ay * t * t * t) + (by * t *t) + (cy * t) + y1;
//System.out.println("x: " + x + " y: " + y + " t: " + t);
points[j] = new Point2D.Double(x,y);
}
return points;
}
private double controlPoint(double p1, double p2, double factor){
double sa = p2 + smooth_factor * (p2 -p1);
double sb = (p2+ sa)/2;
double m = (p2+ factor)/2;
return (sb + m)/2;
}
/**
* Returns the numebr of samples used to calculate the smooth line.
* @return the number of samples.
*/
public int getSamples(){
return this.samples;
}
/**
* Sets the number of samples to be used when calculating the smooth line.
* @param samples the new number of samples (by default is 100)
*/
public void setSamples(int samples){
this.samples = samples;
}
/**
* Returns the smooth factor that is set to be used for calculating the Bezier curves.
* @return the smooth factor.
*/
public double getSmooth_factor(){
return this.smooth_factor;
}
/**
* Sets the smooth factor that will be used to calculate the Bezier curves.
* @param samples the new smooth factor (by default is 0.75)
*/
public void setSmooth_factor(double smooth_factor){
this.smooth_factor = smooth_factor;
}
/**
* Returns either the points entered by the user (if the Point2D[] where passed through the contructor) or the calculated Point2D[] if another option was used.
* @return The Point2d array that will be used to calculate the Bezier curves
*/
public Point2D[] getGivenPoints(){
return this.points;
}
}An example from the JFreeChart using a TimeSeries:
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* -------------------
* TimeSeriesDemo.java
* -------------------
* (C) Copyright 2002-2005, by Object Refinery Limited.
*
*/
import java.awt.Color;
import java.text.SimpleDateFormat;
import javax.swing.JPanel;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYItemRenderer;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.time.*;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.XYDataset;
import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RectangleInsets;
import org.jfree.ui.RefineryUtilities;
/**
* An example of a time series chart. For the most part, default settings are
* used, except that the renderer is modified to show filled shapes (as well as
* lines) at each data point.
* <p>
* IMPORTANT NOTE: THIS DEMO IS DOCUMENTED IN THE JFREECHART DEVELOPER GUIDE.
* DO NOT MAKE CHANGES WITHOUT UPDATING THE GUIDE ALSO!!
*/
public class TimeSeriesDemo1 extends ApplicationFrame {
/**
* A demonstration application showing how to create a simple time series
* chart. This example uses monthly data.
*
* @param title the frame title.
*/
public TimeSeriesDemo1(String title) {
super(title);
XYDataset dataset = createDataset();
JFreeChart chart = createChart(dataset);
ChartPanel chartPanel = new ChartPanel(chart);
chartPanel.setPreferredSize(new java.awt.Dimension(900, 670));
chartPanel.setMouseZoomable(true, false);
setContentPane(chartPanel);
}
/**
* Creates a chart.
*
* @param dataset a dataset.
*
* @return A chart.
*/
private static JFreeChart createChart(XYDataset dataset) {
JFreeChart chart = ChartFactory.createTimeSeriesChart(
"Legal & General Unit Trust Prices", // title
"Date", // x-axis label
"Price Per Unit", // y-axis label
dataset, // data
true, // create legend?
true, // generate tooltips?
false // generate URLs?
);
chart.setBackgroundPaint(Color.white);
XYPlot plot = (XYPlot) chart.getPlot();
plot.setBackgroundPaint(Color.lightGray);
plot.setDomainGridlinePaint(Color.white);
plot.setRangeGridlinePaint(Color.white);
plot.setAxisOffset(new RectangleInsets(5.0, 5.0, 5.0, 5.0));
plot.setDomainCrosshairVisible(true);
plot.setRangeCrosshairVisible(true);
XYItemRenderer r = plot.getRenderer();
/* if (r instanceof XYLineAndShapeRenderer) {
XYLineAndShapeRenderer renderer = (XYLineAndShapeRenderer) r;
renderer.setShapesVisible(true);
renderer.setShapesFilled(true);
}*/
DateAxis axis = (DateAxis) plot.getDomainAxis();
axis.setDateFormatOverride(new SimpleDateFormat("MMM-yyyy"));
return chart;
}
/**
* Creates a dataset, consisting of two series of monthly data.
*
* @return the dataset.
*/
private static XYDataset createDataset() {
TimeSeries s1 = new TimeSeries("L&G European Index Trust", Month.class);
s1.add(new Month(2, 2001), 181.8);
s1.add(new Month(3, 2001), 167.3);
s1.add(new Month(4, 2001), 153.8);
s1.add(new Month(5, 2001), 167.6);
s1.add(new Month(6, 2001), 158.8);
s1.add(new Month(7, 2001), 148.3);
s1.add(new Month(8, 2001), 153.9);
s1.add(new Month(9, 2001), 142.7);
s1.add(new Month(10, 2001), 123.2);
s1.add(new Month(11, 2001), 131.8);
s1.add(new Month(12, 2001), 139.6);
s1.add(new Month(1, 2002), 142.9);
s1.add(new Month(2, 2002), 138.7);
s1.add(new Month(3, 2002), 137.3);
s1.add(new Month(4, 2002), 143.9);
s1.add(new Month(5, 2002), 139.8);
s1.add(new Month(6, 2002), 137.0);
s1.add(new Month(7, 2002), 132.8);
TimeSeries s2 = new TimeSeries("L&G UK Index Trust", Month.class);
s2.add(new Month(2, 2001), 129.6);
s2.add(new Month(3, 2001), 123.2);
s2.add(new Month(4, 2001), 117.2);
s2.add(new Month(5, 2001), 124.1);
s2.add(new Month(6, 2001), 122.6);
s2.add(new Month(7, 2001), 119.2);
s2.add(new Month(8, 2001), 116.5);
s2.add(new Month(9, 2001), 90.7);
s2.add(new Month(10, 2001), 114.5);
s2.add(new Month(11, 2001), 106.1);
s2.add(new Month(12, 2001), 110.3);
s2.add(new Month(1, 2002), 111.7);
s2.add(new Month(2, 2002), 111.0);
s2.add(new Month(3, 2002), 109.6);
s2.add(new Month(4, 2002), 113.2);
s2.add(new Month(5, 2002), 111.6);
s2.add(new Month(6, 2002), 108.8);
s2.add(new Month(7, 2002), 101.6);
/***************************************/
/* Create the smooth timeseries */
/***************************************/
SmoothLine sl = new SmoothLine(s2);
sl.setSamples(300);
sl.setSmooth_factor(0.5);
/**********************/
TimeSeriesCollection dataset = new TimeSeriesCollection();
dataset.addSeries(s1);
dataset.addSeries(s2);
//Add the smooth timeseries
dataset.addSeries(sl.getTimeSeries("Bezier"));
dataset.setDomainIsPointsInTime(true);
return dataset;
}
/**
* Creates a panel for the demo (used by SuperDemo.java).
*
* @return A panel.
*/
public static JPanel createDemoPanel() {
JFreeChart chart = createChart(createDataset());
return new ChartPanel(chart);
}
/**
* Starting point for the demonstration application.
*
* @param args ignored.
*/
public static void main(String[] args) {
TimeSeriesDemo1 demo = new TimeSeriesDemo1("Time Series Demo 1");
demo.pack();
RefineryUtilities.centerFrameOnScreen(demo);
demo.setVisible(true);
}
}