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Appendix B - Creating and compiling a KavaChart program

Compiling a KavaChart Program

To compile a KavaChart program, you must have a standard JDK (version 1.0.2 or version 1.1) or another Java compiler, such as those found in Microsoft's Visual J++, Symantec Cafe, IBM VisualAge, and so on. Your Java compiler will locate the KavaChart classes if you include their location (or zip file) in your CLASSPATH environment variable.

A number of sample KavaChart programs are included with this release in the javachart/demos directory. The programs in this directory serve as a useful set of templates for adding KavaChart graphics to any Java program.

KavaChart programs, whether applets or applications, always draw to a java.awt.Graphics class. They generally draw to a subclass of Java's java.awt.Component class, and require a Component to draw rotated labels, such as those found on axes and bars.

Here is a simple KavaChart program, with comments that describe each step.

import javachart.chart.*;
import java.awt.*;
import java.util.Vector;

public class SimpleChart extends java.awt.Frame {

        public Chart                    chart;

        public static void main (String[] args) {

                SimpleChart             f = new SimpleChart();
                double x[] = new double[5];
                double y[] = new double[5];

                //fill an array with random numbers
                for (int i = 0; i < 5; i++) {
                x[i] = (double) i;
                y[i] = Math.random();
                }

                //create a new BarChart instance
                f.chart = new BarChart("Test Chart");

                //add the random numbers as a dataset with the name "Test"
                f.chart.addDataSet("Test", x, y);

                //Define some axis titles
                f.chart.getXAxis().setTitleString("X axis");
                f.chart.getYAxis().setTitleString("Y axis");

                f.resize(500, 300);
                //resize the chart to be the same size as this Frame
                f.chart.resize(500, 300);
                f.show();
        } 

        public void paint(Graphics g){
                //draw the graph as part of the paint process
                chart.drawGraph(g);
        }
}
To compile this program with Javasoft's JDK, you would execute the following command: To run the program with Javasoft's JDK, you would run the program as follows: Assuming you have KavaChart installed on your system and you have set your CLASSPATH variable correctly, these commands will create and execute a simple KavaChart program, creating a chart that looks like this:

To change this chart from a LineChart to a BarChart or PieChart, you could simply change the following line:

                //f.chart = new BarChart("Test Chart");
                f.chart = new LineChart("Test Chart");

Note: if you're using the SimpleChart example in KavaChart's "standalone" directory, you'll have to run "javachart.standalone.SimpleChart", because these files have been placed into a Java package.



Creating an applet

KavaChart's applet package has a wide range of applets that take advantage of most of KavaChart's functionality. You can easily create a very functional applet with your own capabilities by extending one of the applet source code files. If you'd prefer to create a simpler applet, you can start with a skeleton that looks like this:
import java.applet.*;
import java.awt.Graphics;
import javachart.chart.*;

public class simpleApp extends Applet {

ChartInterface chart;

        public void init () {
                          
                double yvals[] = new double[5];
                for(int i=0;i < 5;i++)
                        yvals[i] = Math.random();
                chart = new BarChart("My Chart");
                chart.resize(this.size().width, this.size().height);
                chart.addDataSet("my data", yvals);
        }

        public void paint(Graphics g) {
                chart.drawGraph(g);
        }
}
Compile this applet as you would any other Java class, and reference it within your HTML code like this:
        <applet code=simpleApp width=400 height=400>
        </applet>
You can also use the "CODEBASE" parameter to point to the directory that contains your applet and "javachart" directory. This can also point to a zip file containing KavaChart classes.

Additional Resources

You can stay current with KavaChart developments by visiting Visual Engineering's web site at www.ve.com. If you have purchased a software maintenance subscription, you will also receive periodic e-mail messages to alert you to new software releases available by password from Visual Engineering's ftp site.

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