Visualizing a tree
The following code sample (VisualizeJ48.java) takes an ARFF file as input, trains a [J48](https://weka.sourceforge.io/doc/weka/classifiers/trees/j48.html) and displays the generated tree with the [TreeVisualizer](https://weka.sourceforge.io/doc/weka/gui/treevisualizer/treevisualizer.html) class.
This can be done with all classifiers that implement the [weka.core.Drawable](https://weka.sourceforge.io/doc/weka/core/drawable.html) interface.
Source code#
import java.awt.BorderLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedReader;
import java.io.FileReader;
import javax.swing.JFrame;
import weka.classifiers.trees.J48;
import weka.core.Instances;
import weka.gui.treevisualizer.PlaceNode2;
import weka.gui.treevisualizer.TreeVisualizer;
/**
* Displays a trained J48 as tree.
* Expects an ARFF filename as first argument.
*
* @author FracPete (fracpete at waikato dot ac dot nz)
*/
public class VisualizeJ48 {
public static void main(String args[]) throws Exception {
// train classifier
J48 cls = new J48();
Instances data = new Instances(new BufferedReader(new FileReader(args[0])));
data.setClassIndex(data.numAttributes() - 1);
cls.buildClassifier(data);
// display classifier
final javax.swing.JFrame jf =
new javax.swing.JFrame("Weka Classifier Tree Visualizer: J48");
jf.setSize(500,400);
jf.getContentPane().setLayout(new BorderLayout());
TreeVisualizer tv = new TreeVisualizer(null,
cls.graph(),
new PlaceNode2());
jf.getContentPane().add(tv, BorderLayout.CENTER);
jf.addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent e) {
jf.dispose();
}
});
jf.setVisible(true);
tv.fitToScreen();
}
}