Documentation

If you have not already done so, copy the files for this example as follows:

1. Copy the following folder that ships with MATLAB to your work folder:

   matlabroot\toolbox\javabuilder\Examples\PlotExample
   

2. At the MATLAB command prompt, cd to the new PlotExample subfolder in your work folder.

If you have not already done so, set the environment variables that are required on a development machine. See Configure Your Java Environment.

Write the drawplot.m function as you would any MATLAB function.

The following code defines the drawplot.m function:

function drawplot(x,y)
plot(x,y);

This code is already in your work folder in PlotExample\PlotDemoComp\drawplot.m.

While in MATLAB, issue the following command to open the Library Compiler app:

libraryCompiler

You create a Java package by using the Library Compiler app to build a Java class that wraps around your MATLAB code.

To create the Java package the Library Compiler app, use the following information as you work through this example in Compile Java Packages with Library Compiler App:

Write source code for an application that accesses the MATLAB function.

The sample application for this example is in matlabroot\toolbox\javabuilder\Examples\PlotExample\PlotDemoJavaApp\createplot.java.

The program graphs a simple parabola from the equation y = x² .

The program listing is shown here.

 createplot.java

/* Necessary package imports */
import com.mathworks.toolbox.javabuilder.*;
import plotdemo.*;

/*
 * createplot class demonstrates plotting x-y data into 
 * a MATLAB figure window by graphing a simple parabola.
 */
class createplot
{
   public static void main(String[] args)
   {
      MWNumericArray x = null;   /* Array of x values */
      MWNumericArray y = null;   /* Array of y values */
      plotter thePlot = null;    /* Plotter class instance */
      int n = 20;                /* Number of points to plot */

      try
      {
         /* Allocate arrays for x and y values */
         int[] dims = {1, n};
         x = MWNumericArray.newInstance(dims, 
            MWClassID.DOUBLE, MWComplexity.REAL);
         y = MWNumericArray.newInstance(dims, 
            MWClassID.DOUBLE, MWComplexity.REAL);

         /* Set values so that y = x^2 */
         for (int i = 1; i <= n; i++)
         {
            x.set(i, i);
            y.set(i, i*i);
         }

         /* Create new plotter object */
         thePlot = new plotter();

         /* Plot data */
         thePlot.drawplot(x, y);
         thePlot.waitForFigures(); 
      }

      catch (Exception e)
      {
         System.out.println("Exception: " + e.toString());
      }

      finally
      {
         /* Free native resources */
         MWArray.disposeArray(x);
         MWArray.disposeArray(y);
         if (thePlot != null)
            thePlot.dispose();
      }
   }
}

The program does the following:

Compile the createplot application using javac. When entering this command, ensure there are no spaces between path names in the matlabroot argument. For example, there should be no space between javabuilder.jar; and .\distrib\plotdemo.jar in the following example. cd to your work folder. Ensure createplot.java is in your work folder

Run the application.

To run the createplot.class file, do one of the following:

version -java

The createplot program should display the output.