13.11 (Plot the square function) Write a program that draws a diagram for the function f(x) = x2 (see Figure 13.29c).

Exercise13_11.java

/*
 * *13.11 (Plot the square function) Write a program that draws a diagram for the function
 * f(x) = x2 (see Figure 13.29c).
 *
 * Hint: Add points to a polygon p using the following loop:
 * 
 * double scaleFactor = 0.1;
 * for (int x = -100; x <= 100; x++) {
 *     p.addPoint(x + 200, 200 - (int)(scaleFactor * x * x));
 *  }
 *
 * Connect the points using g.drawPolyline(p.xpoints, p.ypoints,
 * p.npoints) for a Graphics object g. p.xpoints returns an array of xcoordinates,
 * p.ypoints an array of y-coordinates, and p.npoints the number
 * of points in Polygon object p.
 */

import java.awt.*;
import javax.swing.*;

public class Test extends JFrame {
    
    public Test() {
        setLayout(new BorderLayout());
        add(new MyPanel(), BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        JFrame frame = new Test();
        frame.setSize(400, 300);
        frame.setTitle("Exercise13_10");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setVisible(true);
    }
}

class MyPanel extends JPanel {

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        // Draw lines
        g.drawLine(10, 240, 380, 240);
        g.drawLine(200, 10, 200, 300);
        
        // Create polygon for adding points
        Polygon p = new Polygon();
        
        double scaleFactor = 0.1;
        
        for (int x = -100; x <= 100; x++)
            p.addPoint(x + 200, 200 - (int)(scaleFactor * x * x / 10) + 40);
        
        g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
    }
}