Java Java --> Plotting Two Curves on the same Plot

[jedishrfu]

Here's a Java program that uses Java Swing and Java AWT to plot sine and cosine curves for the interval [0,2π].

The program creates a window with a panel where both curves are drawn:

• Uses JFrame and JPanel for GUI rendering.
• Uses Graphics to draw the sine and cosine curves.
• Automatically scales the graph to fit within the window.

Java Code:​

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

public class SineCosinePlot extends JPanel {

    private static final int WIDTH = 800;  // Width of the panel
    private static final int HEIGHT = 600; // Height of the panel
    private static final int PADDING = 50; // Padding around the graph
    private static final double SCALE_X = WIDTH / (2 * Math.PI); // Scaling factor for x-axis
    private static final double SCALE_Y = HEIGHT / 3; // Scaling factor for y-axis

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        drawAxes(g);
        drawSineCurve(g);
        drawCosineCurve(g);
    }

    private void drawAxes(Graphics g) {
        g.setColor(Color.BLACK);
        int xAxisY = HEIGHT / 2;
        int yAxisX = PADDING;
   
        // X-axis
        g.drawLine(PADDING, xAxisY, WIDTH - PADDING, xAxisY);
   
        // Y-axis
        g.drawLine(yAxisX, PADDING, yAxisX, HEIGHT - PADDING);
   
        // Labels
        g.drawString("0", yAxisX - 10, xAxisY + 15);
        g.drawString("π", (int) (SCALE_X * Math.PI) + PADDING - 5, xAxisY + 15);
        g.drawString("2π", (int) (SCALE_X * 2 * Math.PI) + PADDING - 5, xAxisY + 15);
        g.drawString("1", yAxisX - 20, xAxisY - (int) (SCALE_Y));
        g.drawString("-1", yAxisX - 20, xAxisY + (int) (SCALE_Y));
    }

    private void drawSineCurve(Graphics g) {
        g.setColor(Color.RED);
        for (int i = 0; i < WIDTH - PADDING * 2; i++) {
            double x1 = (i / SCALE_X);
            double y1 = Math.sin(x1);
            double x2 = ((i + 1) / SCALE_X);
            double y2 = Math.sin(x2);

            int screenX1 = i + PADDING;
            int screenY1 = HEIGHT / 2 - (int) (y1 * SCALE_Y);
            int screenX2 = i + 1 + PADDING;
            int screenY2 = HEIGHT / 2 - (int) (y2 * SCALE_Y);

            g.drawLine(screenX1, screenY1, screenX2, screenY2);
        }
    }

    private void drawCosineCurve(Graphics g) {
        g.setColor(Color.BLUE);
        for (int i = 0; i < WIDTH - PADDING * 2; i++) {
            double x1 = (i / SCALE_X);
            double y1 = Math.cos(x1);
            double x2 = ((i + 1) / SCALE_X);
            double y2 = Math.cos(x2);

            int screenX1 = i + PADDING;
            int screenY1 = HEIGHT / 2 - (int) (y1 * SCALE_Y);
            int screenX2 = i + 1 + PADDING;
            int screenY2 = HEIGHT / 2 - (int) (y2 * SCALE_Y);

            g.drawLine(screenX1, screenY1, screenX2, screenY2);
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Sine and Cosine Plot");
        SineCosinePlot panel = new SineCosinePlot();
        frame.add(panel);
        frame.setSize(WIDTH, HEIGHT);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Explanation:​

1. paintComponent(Graphics g):
   • This method is overridden when drawing the sine and cosine curves.
2. Axes Drawing:
   • Draws the x-axis and y-axis with labels for 0,𝜋, and 2𝜋.
3. Sine and Cosine Curves:
   • The graph is drawn by iterating over screen pixels and mapping them to the sine/cosine function.
   • x values are scaled using SCALE_X, and
   • y values are scaled using SCALE_Y.
   • drawLine() is used to connect consecutive points smoothly.

​

Output:​

• A red sine wave and a blue cosine wave are displayed in a window.
• Axes labeled at 0,𝜋, and 2𝜋.
• The graph scales dynamically to fit in the window.

Solution Credits​

Proposed by: @hagopbul
Coded by: @ChatGPT
Reviewed by: @jedishrfu