JFreeChart（四）之线型图

转载自 JFreeChart线型图

线图或折线图来显示信息为一系列由直线段连接的数据点(标记)。线图显示数据在相同的时间频率如何变化。本章从一个给定的业务数据演示如何使用JFreeChart创建线型图。

业务数据

下面的示例绘制折线图显示从1970年开始学校在不同年份开通数量。

给定的数据如下：

年份	学校数量
1970	15
1980	30
1990	60
2000	120
2013	240
2014	300

基于AWT的应用

以下是对从上述给定的信息创建线型图的代码。此代码可以帮助在AWT的应用程序嵌入一个折线图。

import org.jfree.chart.ChartPanel;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RefineryUtilities;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.category.DefaultCategoryDataset;public class LineChart_AWT extends ApplicationFrame
{public LineChart_AWT( String applicationTitle , String chartTitle ){super(applicationTitle);JFreeChart lineChart = ChartFactory.createLineChart(chartTitle,"Years","Number of Schools",createDataset(),PlotOrientation.VERTICAL,true,true,false);ChartPanel chartPanel = new ChartPanel( lineChart );chartPanel.setPreferredSize( new java.awt.Dimension( 560 , 367 ) );setContentPane( chartPanel );}private DefaultCategoryDataset createDataset( ){DefaultCategoryDataset dataset = new DefaultCategoryDataset( );dataset.addValue( 15 , "schools" , "1970" );dataset.addValue( 30 , "schools" , "1980" );dataset.addValue( 60 , "schools" ,  "1990" );dataset.addValue( 120 , "schools" , "2000" );dataset.addValue( 240 , "schools" , "2010" );dataset.addValue( 300 , "schools" , "2014" );return dataset;}public static void main( String[ ] args ) {LineChart_AWT chart = new LineChart_AWT("School Vs Years" ,"Numer of Schools vs years");chart.pack( );RefineryUtilities.centerFrameOnScreen( chart );chart.setVisible( true );}
}

保存LineChart_AWT.java文件如上面的Java代码，然后从命令提示符下编译并运行它，如下所示：

$javac LineChart_AWT.java 
$java LineChart_AWT

如果一切顺利，它会编译并运行生成以下线图：

创建JPEG图像

让我们重新编写上面的例子，在命令行执行生成JPEG图像。

import java.io.*;
import org.jfree.chart.JFreeChart; 
import org.jfree.chart.ChartFactory; 
import org.jfree.chart.ChartUtilities; 
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.category.DefaultCategoryDataset;public class LineChart
{public static void main( String[ ] args ) throws Exception{DefaultCategoryDataset line_chart_dataset = new DefaultCategoryDataset();line_chart_dataset.addValue( 15 , "schools" , "1970" );line_chart_dataset.addValue( 30 , "schools" , "1980" );line_chart_dataset.addValue( 60 , "schools" , "1990" );line_chart_dataset.addValue( 120 , "schools" , "2000" );line_chart_dataset.addValue( 240 , "schools" , "2010" ); line_chart_dataset.addValue( 300 , "schools" , "2014" );JFreeChart lineChartObject = ChartFactory.createLineChart("Schools Vs Years","Year","Schools Count",line_chart_dataset,PlotOrientation.VERTICAL,true,true,false);int width = 640; /* Width of the image */int height = 480; /* Height of the image */ File lineChart = new File( "LineChart.jpeg" ); ChartUtilities.saveChartAsJPEG(lineChart ,lineChartObject, width ,height);}
}

让我们保存LineChart.java文件如上面的Java代码，然后从命令提示符下编译并运行它，如下所示：