CODEWITHSUNDEEP
javagraphtrigonometry
CodeNewbie
CodeNewbie

Reputation: 57

Java sine and cosine

Hello I am trying to create a java program that allows you to graph an equation and its been working well so far until I wanted it to graph cosine and sine functions. I am confused on how I can do this when sine and cosine return doubles but drawLine only takes in integers. I am new to java so this may be easy but if you could help I would appreciate it.

Here is my code: 

import java.util.Scanner;
import javax.swing.JFrame;
import javax.swing.*;
import java.awt.*;
import java.lang.Math;
import java.awt.geom.*;

class PlotGraph extends JFrame{


public void paintComponent(Graphics g){
    Graphics2D g2 = (Graphics2D) g;

    g.drawLine(50, 300, 550, 300); //x axis
    g.drawLine(300, 550, 300, 50); //y axis
    //Orignin x = 300 y = 300

    double xmin, xmax;
    double y;
    xmin =(0);
    xmax = 100;
    double x = xmin;

    double form = Math.cos(x);

    double last_y = 300-(form);

    for (x = xmin+1; x<=xmax; x++){
    double newForm = Math.cos(x);
    y = 300-(newForm);
    g2.draw(new Line2D.Double(x-1+(300), last_y, x+300, y));
    last_y = y;

    }




}

public static void main(String [] args) {

    PlotGraph graph = new PlotGraph();
    graph.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    graph.setSize(600, 600);
    graph.setVisible(true); 
    graph.setTitle("PlotGraph");

}
}

Upvotes: 0

Views: 4798

Answers (4)

Breavyn
Breavyn

Reputation: 2242

Try casting the double to an int.

int y = 300 - (int) (Math.cos(x) * scaleFactor);

And as Aiias said: cos will only return values between -1 and 1. So make sure you multiply it by a constant factor or you will lose the value after casting.

Upvotes: 0

Bohemian
Bohemian

Reputation: 425198

Since Math.cos() returns a value between -1 and 1, casting to int will result in only 3 values -1, 0 and 1, and will almost always be 0.

What you want to do is multiply the double by a large constant to create a range of integers:

    y = 300-(int)(300d * newForm);

Note the "d" after the 300: that makes the 300 a double, making the result if the multiplication also double, this keeping fine granularity.

Upvotes: 2

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285405

Use Line2D.Double objects, a Graphics2D Graphics object and have the Graphics2D object draw the shape with its draw(...) method.

Upvotes: 1

Richard Sitze
Richard Sitze

Reputation: 8463

After properly scaling, you might try either of:

  • typecast the double to an int: int i = (int)d;

  • rounding, which returns long which must by typecast to int: int i = (int)Math.round(d);

Upvotes: 0

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