Why applet does not draw trigonometric funtion's graph correctly?

Question

I am a beginner in Java Swing . I was trying to draw the graph of sin(x) in applet . I am surprised why applet always draws my axis only not my graph? here is my code :

import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;

public class NewApplet extends Applet
{

    public void init()
    {
        // TODO start asynchronous download of heavy resources
    }
    public void paint(Graphics g)
    {
    Graphics2D g2 = (Graphics2D) g;
    //get dimension
    Dimension appletSize = this.getSize();
    // make the applet empty at start
    g2.setBackground(Color.white);
    g2.setColor(Color.white);
    g2.fillRect(0, 0, appletSize.width, appletSize.height);
    //now draw all you need
    g2.setColor(Color.red);
    //x axis
    g2.drawLine(0, appletSize.height/2, appletSize.width, appletSize.height/2);
    //y axis
    g2.drawLine(appletSize.width/2, 0, appletSize.width/2, appletSize.height);
    //function
    g2.setColor(Color.black);
    for(int k=0; k<=180; k++)
    {
        g2.drawString(".", (float) Math.toRadians(k), (float) Math.sin(Math.toRadians(k)));
    }
}
}

I am plotting 180 points of sin(x) with String "." , but My applet didn't show a single plot.Why?

[ Mention if there any good practice I should follow or suggest me any good library (JAR) for drawing graphs ]

Answer 1

It actually draws a graph.

Since values sine are between -1 and +1, and the radian values are between0 +π and -π, so the graph is drawn at those coordinates.

If you change this line:

g2.drawString(".", (float) Math.toRadians(k), (float) Math.sin(Math.toRadians(k)));

to this line:

g2.drawString(".", (appletSize.height/2)+(float) Math.toRadians(k)*50, (appletSize.width/2)+(float) Math.sin(Math.toRadians(k))*50);

You will see half the graph (since you have written the code for half the graph.)

Here:

• I add (appletSize.height/2) and (appletSize.width/2) to the values, to bring them to the center of the screen (on the graph)
• I multiply them by 50 to make the graph large, else, the graph is too small to understand.