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How to draw a graph in Java applet

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Join Date: Jun 2008

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Re: How to draw a graph in Java applet

#11

Jun 4th, 2008

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Originally Posted by Software guy

Thanks for your replies , i really wasn't expecting so many replies for my simple question.Because of your explanation in detail i understood it properly.Mathematically Alex is 100% right , because it really gives me a gradient of zero which is literally a straight line. I have changed my code and it gives me a sine curve but , it sticks to the top of the window but i hope that can be figured out . Once again thanks for the help and thanks for supporting the idea that g.drawLine(i,i,i,i) represents a point .Hopefully i ill be posting the code when its all done

I wish I could help you with using more of the Graphics class's functions but unfortunately I truly HATE using Graphics from getGraphics in containers. I wouldn't be able to help you with setting the location of your Graphics object.

I personally prefer using GObjects, GCompounds, GLines that work on GCanvases.

The only method I have an issue with understanding is the move method in most GObject classes. I'm almost certain that it fires a thread that continuously offsets the object but i could be wrong.

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Re: How to draw a graph in Java applet

#12

Jun 4th, 2008

import java.awt.*;
import java.applet.*;

public class graphic extends Applet {
Button button1;
public void init() {
}

public void paint(Graphics g) {

int CYCLE=4;
int MAX = 1000;
int x1=0;
int x2=0;
g.setColor(Color.red);//color for axes
g.drawLine(0,150,700,150);//x-axis
g.drawLine(240,0,240,500);//y-axis
g.drawString("X-Axis", 430,140);//Label for x-axis
g.drawString("Y-Axis",200,270);//Label for y-axis
g.setColor(Color.blue);//color for the sin curve

for (int i=-130;i<=368;i++)
{
try
{
Thread.sleep(10); // 10 millisecond delay
}
catch(InterruptedException e)
{
e.printStackTrace();
}

x1 = (int)(100 * Math.sin(((i)*2*Math.PI*CYCLE)/(MAX)));
x2 = (int)(100 * Math.sin(((i+1)*2*Math.PI*CYCLE)/(MAX)));
g.drawLine(i+121,x1+138,(i+1)+121,x2+138);
}
g.setFont(new Font("Times New Roman",Font.BOLD,15));
g.drawString("IT WORKS ; )",100,50); }
}
//Here is the code

Last edited by Software guy; Jun 4th, 2008 at 8:52 pm.

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Re: How to draw a graph in Java applet

#13

Jun 4th, 2008

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Originally Posted by Software guy

import java.awt.*;
import java.applet.*;

public class graphic extends Applet {
Button button1;
public void init() {
}

public void paint(Graphics g) {

int CYCLE=4;
int MAX = 1000;
int x1=0;
int x2=0;
g.setColor(Color.red);//color for axes
g.drawLine(0,150,700,150);//x-axis
g.drawLine(240,0,240,500);//y-axis
g.drawString("X-Axis", 430,140);//Label for x-axis
g.drawString("Y-Axis",200,270);//Label for y-axis
g.setColor(Color.blue);//color for the sin curve

for (int i=-130;i<=368;i++)
{
try
{
Thread.sleep(10); // 10 millisecond delay
}
catch(InterruptedException e)
{
e.printStackTrace();
}

x1 = (int)(100 * Math.sin(((i)*2*Math.PI*CYCLE)/(MAX)));
x2 = (int)(100 * Math.sin(((i+1)*2*Math.PI*CYCLE)/(MAX)));
g.drawLine(i+121,x1+138,(i+1)+121,x2+138);
}
g.setFont(new Font("Times New Roman",Font.BOLD,15));
g.drawString("IT WORKS ; )",100,50); }
}
//Here is the code

 Help with Code Tags 
 java Syntax (Toggle Plain Text) 
import java.awt.*;
import java.applet.*;
 
public class graphic extends Applet {
	Button button1;
	public void init() {
	}
 
	public void paint(Graphics g) {
 
        int CYCLE=4;
        int MAX = 1000;
        int WEIGHT = 100;
		int x1=0;
		int x2=0;
		g.setColor(Color.red);//color for axes
		g.drawLine(0,150,700,150);//x-axis
        g.drawLine(240,0,240,500);//y-axis
        g.drawString("X-Axis", 430,140);//Label for x-axis
        g.drawString("Y-Axis",200,270);//Label for y-axis
        g.setColor(Color.blue);//color for the sin curve
 
         for (int i=-130;i<=368;i++)
       {  	  
       	try 
            {
           Thread.sleep(10); // 10 millisecond delay 
            } 
            catch(InterruptedException e)
            {
           e.printStackTrace();
            } 
 
       	x1 = (int)(WEIGHT * Math.sin(((i)*2*Math.PI*CYCLE)/(MAX)));
       	x2 = (int)(WEIGHT * Math.sin(((i+1)*2*Math.PI*CYCLE)/(MAX)));  	
       	g.drawLine(i+121,x1+138,(i+1)+121,x2+138);
       }
        g.setFont(new Font("Times New Roman",Font.BOLD,15));
        g.drawString("IT WORKS ; )",100,50);	}	
}
//Here is the code
import java.awt.*;
import java.applet.*;

public class graphic extends Applet {
	Button button1;
	public void init() {
	}

	public void paint(Graphics g) {
     
        int CYCLE=4;
        int MAX = 1000;
        int WEIGHT = 100;
		int x1=0;
		int x2=0;
		g.setColor(Color.red);//color for axes
		g.drawLine(0,150,700,150);//x-axis
        g.drawLine(240,0,240,500);//y-axis
        g.drawString("X-Axis", 430,140);//Label for x-axis
        g.drawString("Y-Axis",200,270);//Label for y-axis
        g.setColor(Color.blue);//color for the sin curve
        
         for (int i=-130;i<=368;i++)
       {  	  
       	try 
            {
           Thread.sleep(10); // 10 millisecond delay 
            } 
            catch(InterruptedException e)
            {
           e.printStackTrace();
            } 
	
       	x1 = (int)(WEIGHT * Math.sin(((i)*2*Math.PI*CYCLE)/(MAX)));
       	x2 = (int)(WEIGHT * Math.sin(((i+1)*2*Math.PI*CYCLE)/(MAX)));  	
       	g.drawLine(i+121,x1+138,(i+1)+121,x2+138);
       }
        g.setFont(new Font("Times New Roman",Font.BOLD,15));
        g.drawString("IT WORKS ; )",100,50);	}	
}
//Here is the code

Keep in mind that the MAX is really the maximum difference between the min-x and max-x values.

For example, if you can go from -100 to 100 in your graph, MAX should be the difference of the two, resulting in MAX = 200

Edit: Added an int named WEIGHT that controls the peak and valley of your sin graph. The greater the WEIGHT the deeper and steeper your waves, the lower the WEIGHT the more subtle your graph will be.

Last edited by Alex Edwards; Jun 4th, 2008 at 11:54 pm.

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PoovenM

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Re: How to draw a graph in Java applet

#14

Jun 6th, 2008

Alex said:

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There is no rate of change in his function as i increments. Basically the graph isn't dependent on i, so he ends up with a constant graph, or a straight line.

Well that's not exactly true; the gradient (i.e. rate of change) of a Sin curve depends on the input. Though I did misread the part about the circle, my bad

Good work Alex

Though because of the nature of a Sin graph, one did not have to consider the changed between graphics and the Cartesian plane. On the screen y increases as we move down, however, on the Cartesian plane, y increase as we move up. Something to consider if ever you needed to draw, say a straight line.

So perhaps mark this post as Solved