TimeSeries 图表（TimeSeries Chart）

时间序列图表显示数据点序列，它们以相等的时间间隔变化。 本章演示了如何使用JFreeChart从给定的业务数据集创建Time Series Chart 。

业务数据

让我们考虑使用标准Java API Math.random()生成的各种随机数。 我们使用这些数字来生成时间序列图表。 您可以在给定的时间间隔内为网站中发生的错误总数生成类似的图表。

基于AWT的应用 (AWT Based Application)

以下是在给定时间内部由Math.random()生成的数字创建时间序列图表的代码。

import org.jfree.chart.ChartFactory; 
import org.jfree.chart.ChartPanel; 
import org.jfree.chart.JFreeChart; 
import org.jfree.data.general.SeriesException; 
import org.jfree.data.time.Second; 
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.RefineryUtilities;
public class TimeSeries_AWT extends ApplicationFrame {
   public TimeSeries_AWT( final String title ) {
      super( title );         
      final XYDataset dataset = createDataset( );         
      final JFreeChart chart = createChart( dataset );         
      final ChartPanel chartPanel = new ChartPanel( chart );         
      chartPanel.setPreferredSize( new java.awt.Dimension( 560 , 370 ) );         
      chartPanel.setMouseZoomable( true , false );         
      setContentPane( chartPanel );
   }
   private XYDataset createDataset( ) {
      final TimeSeries series = new TimeSeries( "Random Data" );         
      Second current = new Second( );         
      double value = 100.0;         
      for (int i = 0; i < 4000; i++) {
         try {
            value = value + Math.random( ) - 0.5;                 
            series.add(current, new Double( value ) );                 
            current = ( Second ) current.next( ); 
         } catch ( SeriesException e ) {
            System.err.println("Error adding to series");
         }
      }
      return new TimeSeriesCollection(series);
   }     
   private JFreeChart createChart( final XYDataset dataset ) {
      return ChartFactory.createTimeSeriesChart(             
         "Computing Test", 
         "Seconds",              
         "Value",              
         dataset,             
         false,              
         false,              
         false);
   }
   public static void main( final String[ ] args ) {
      final String title = "Time Series Management";         
      final TimeSeries_AWT demo = new TimeSeries_AWT( title );         
      demo.pack( );         
      RefineryUtilities.positionFrameRandomly( demo );         
      demo.setVisible( true );
   }
}   

让我们将上述Java代码保存在TimeSeries_AWT.java文件中，然后从提示命令编译并运行它 -

$javac TimeSeries_AWT.java  
$java TImeSeries_AWT 

如果一切正常，它将编译并运行以生成以下时间序列图 -

JPEG图像创建 (JPEG Image Creation)

让我们重新编写上面的例子，从命令行生成JPEG图像。

import java.io.*;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.data.general.SeriesException;
import org.jfree.data.time.Second;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.XYDataset;
import org.jfree.chart.ChartUtilities;
public class TimeSeriesChart {
   public static void main( final String[ ] args )throws Exception {
      final TimeSeries series = new TimeSeries( "Random Data" );
      Second current = new Second();
      double value = 100.0;
      for ( int i = 0 ; i < 4000 ; i++ ) {
         try {
            value = value + Math.random( ) - 0.5;
            series.add( current , new Double( value ) );
            current = ( Second ) current.next( );
         } catch ( SeriesException e ) {
            System.err.println( "Error adding to series" );
         }
      }
      final XYDataset dataset=( XYDataset )new TimeSeriesCollection(series);
      JFreeChart timechart = ChartFactory.createTimeSeriesChart(
         "Computing Test", 
         "Seconds", 
         "Value", 
         dataset,
         false, 
         false, 
         false);
      int width = 560;   /* Width of the image */
      int height = 370;  /* Height of the image */ 
      File timeChart = new File( "TimeChart.jpeg" ); 
      ChartUtilities.saveChartAsJPEG( timeChart, timechart, width, height );
   }
}

让我们将上述Java代码保存在TimeSeriesChart.java文件中，然后从命令提示编译并运行它 -

$javac TimeSeriesChart.java  
$java TimeSeriesChart

如果您的环境一切正常，它将编译并运行以在当前目录中创建JPEG图像文件TimeChart.jpeg文件。