JFreeChart - Line Chart


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A line chart or line graph displays information as a series of data points (markers) connected by straight line segments. Line Chart shows how the data changes at equal time frequency. This chapter demonstrates how we can use JFreeChart to create Line Chart from a given set of business data.

Business Data

The following example draws a line chart to show a trend of number of schools opened in different years starting from 1970.

Given data is as follows :

Year Number OF Schools
1970 15
1980 30
1990 60
2000 120
2013 240
2014 300

AWT Based Application

Following is the code to create Line Chart from the above given information. This code helps you embed a line chart in any AWT based application.

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 );
   }
}

Let us keep the above Java code in LineChart_AWT.java file, and then compile and run it from command prompt as follows :

$javac LineChart_AWT.java 
$java LineChart_AWT 

If everything is fine , it will compile and run to generate the following Line Graph :

JFreeChart Line Chart

JPEG Image Creation

Let us re-write above example to generate a JPEG image from command line.

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);
   }
}

Let us keep the above Java code in LineChart.java file, and then compile and run it from command prompt as follows :

$javac LineChart.java 
$java LineChart 

If everything is fine , it will compile and execute to create JPEG image file named LineChart.jpeg in your current directory.



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