折线图或折线图将信息显示为由直线段连接的一系列数据点(标记).折线图显示数据如何以相等的时间频率变化.
本章演示了如何使用JFreeChart从给定的业务数据集创建折线图./p>
以下示例绘制折线图,以显示从1970年开始的不同年份开设的学校数量的趋势.
给定数据如下<
年 | 学校数量 |
---|---|
1970 | 15 |
1980 | 30 |
1990 | 60 |
2000 | 120 |
2013 | 240 |
2014 | 300 |
以下是从上面给出的信息创建折线图的代码.此代码可帮助您在任何基于AWT的应用程序中嵌入折线图.
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 ); } }
让我们将上述Java代码保存在 LineChart_AWT.java 文件中,然后从命令提示编译并运行它为 :
$ javac LineChart_AWT.java $ java LineChart_AWT
如果一切正常,它将编译并运行以生成以下折线图 :
让我们重新编写上面的例子来生成一个JPEG图像命令行.
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); } }
让我们将上述Java代码保存在 LineChart.java 文件中,然后从命令提示编译并运行它为 :
$javac LineChart.java $java LineChart
如果一切正常,它将编译并执行以在当前目录中创建名为 LineChart.jpeg 的JPEG图像文件.