line graphs

[Nicole Tan]

how do i display a line graph that have n (x, y) data plotted and a line drawn on it provided the an equation of y = ax^3 + bx^2 + cx^1 + d, given the coefficients a,b,c,d.
preferably in jpanel..

[Eddie Vanda]

Nicole,
Look at overriding JComponent's paintComponent method (you can do that in a JPanel) and the drawLine (...) method in the Graphics class.
Ed

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.text.*;
import javax.swing.*;
import javax.swing.event.*;
 
public class GraphingTest
{
    public static void main(String[]args)
    {
        GraphingPanel gp = new GraphingPanel();
        GraphingSelection selection = new GraphingSelection(gp);
        GraphingInput input = new GraphingInput(gp);
        JFrame f = new JFrame("Graphing Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(selection, "North");
        f.getContentPane().add(gp);
        f.getContentPane().add(input, "South");
        f.setSize(500,500);
        f.setLocation(200,200);
        f.setVisible(true);
     }
}
 
/**
 * Draws the polynomial.
 * Loaded into the center section of the content pane in main method.
 * References in GraphingSelection and GraphingInput allow adjustments
 * to be made in polynomial constants a, b, c and d and in polynomial
 * term selection booleans showCube, showSquare, showLinear and showConstant.
 */
class GraphingPanel extends JPanel
{
    final int PAD = 15;
    NumberFormat nf;
    final int
        A = 0,
        B = 1,
        C = 2,
        D = 3;
    boolean showCube, showSquare, showLinear, showConstant;
    double a, b, c, d;
 
    public GraphingPanel()
    {
        showCube = showSquare = showLinear = showConstant = true;
        a = b = c = d = 0.5;
        nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(2);
        nf.setGroupingUsed(false);
        setBackground(Color.white);
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        // ordinate
        g2.draw(new Line2D.Double(w/2, PAD, w/2, h - PAD));
        float yInc = (h - 2*PAD)/50f;
        float x1 = w/2;
        float y1 = PAD;
        for(int i = 0; i <= 50; i++)
        {
            if(i % 5 == 0)
            {
                g2.draw(new Line2D.Double(x1 - 2, y1, x1 + 2, y1));
                if(i != 25)
                    g2.drawString(String.valueOf(5 - i/5), x1 - 15, y1 + 5);
            }
            else
                g2.draw(new Line2D.Double(x1 - 1, y1, x1, y1));
            y1 += yInc;
        }
        // abcissa
        g2.draw(new Line2D.Double(PAD, h/2, w - PAD, h/2));
        float xInc = (w - 2*PAD)/50f;
        x1 = PAD;
        y1 = h/2;
        for(int i = 0; i <= 50; i++)
        {
            if(i % 5 == 0)
            {
                g2.draw(new Line2D.Double(x1, y1 - 2, x1, y1 + 2));
                if(i != 25)
                    g2.drawString(String.valueOf(i/5 - 5), x1 - 3, y1 + 15);
            }
            else
                g2.draw(new Line2D.Double(x1, y1, x1, y1 + 1));
            x1 += xInc;
        }
        // polynomial
        g2.setPaint(Color.red);
        double cube, square, linear, constant, y;
        double yLast = 0;
        double x = PAD;
        for(int i = -25; i <= 25; i++)
        {
            cube = square = linear = constant = 0;
            if(showCube)
                cube = a * Math.pow(i/5f, 3) * (h/2 - PAD)/5;
            if(showSquare)
                square = b * Math.pow(i/5f, 2) * (h/2 - PAD)/5;
            if(showLinear)
                linear = c * i * (h/2 - PAD)/25;
            if(showConstant)
                constant = d * (h/2 - PAD);
            y = h/2 - (cube + square + linear + constant);
                /*
            if(i == 10)
            {
                System.out.println("y = " + nf.format(y) + "\n" +
                                   "cube = " + nf.format(cube) + "\n" +
                                    nf.format(cube*5/(h/2 - PAD)));
                                //   "square = " + nf.format(square) + "\n" +
                                //   "linear = " + nf.format(linear) + "\n" +
                                //   "constant = " + constant);
                g2.fill(new Ellipse2D.Double(x - 2, y - 2, 4, 4));    
            }
                */
            //g2.fill(new Ellipse2D.Double(x - 2, y - 2, 4, 4));    // marker
            if(i > -25)                                             // no line on
                g2.draw(new Line2D.Double(x - xInc, yLast, x, y));  //   first pass
            x += xInc;
            yLast = y;
        }
    }
 
    public void setSelector(boolean isVisible, int id)
    {
        switch(id)
        {
            case A:
                showCube = isVisible;
                break;
            case B:
                showSquare = isVisible;
                break;
            case C:
                showLinear = isVisible;
                break;
            case D:
                showConstant = isVisible;
        }
        repaint();
    }
 
    public void setConstant(double update, int id)
    {
        switch(id)
        {
            case A:
                a = update;
                break;
            case B:
                b = update;
                break;
            case C:
                c = update;
                break;
            case D:
                d = update;
        }
        repaint();
    }
}
 
/**
 * JRadioButtons allow inclusion/exclusion of the polynomial terms by
 * setting the showCube, showSquare, showLinear and showConstant
 * booleans in GraphingPanel.
 * Loaded into the north section of the content pane in main method.
 */
class GraphingSelection extends JPanel
{
    GraphingPanel graphingPanel;
 
    public GraphingSelection(GraphingPanel gp)
    {
        graphingPanel = gp;
        final JRadioButton
            aButton = new JRadioButton("<html><font size=5>x³</font></html>"),
            bButton = new JRadioButton("<html><font size=5>x²</font></html>"),
            cButton = new JRadioButton("<html><font size=5>x</font></html>"),
            dButton = new JRadioButton();
        ItemListener l = new ItemListener()
        {
            int id;
 
            public void itemStateChanged(ItemEvent e)
            {
                JRadioButton button = (JRadioButton)e.getSource();
                if(button == aButton)
                    id = 0;
                if(button == bButton)
                    id = 1;
                if(button == cButton)
                    id = 2;
                if(button == dButton)
                    id = 3;
                graphingPanel.setSelector(button.isSelected(), id);
            }
        };
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.insets = new Insets(0,2,0,2);
        addComponents(new JLabel("a"), aButton, gbc, l);
        addComponents(new JLabel("b"), bButton, gbc, l);
        addComponents(new JLabel("c"), cButton, gbc, l);
        addComponents(new JLabel("d"), dButton, gbc, l);
    }
 
    private void addComponents(JLabel label, JRadioButton b, GridBagConstraints gbc,
                               ItemListener l)
    {
        gbc.anchor = gbc.EAST;
        add(label,gbc);
        gbc.anchor = gbc.WEST;
        add(b, gbc);
        if(!label.getText().equals("d"))
        {
            gbc.anchor = gbc.CENTER;
            add(new JLabel("+"), gbc);
        }
        b.setSelected(true);
        b.addItemListener(l);
    }
}
 
/**
 * JSpinners allow adjustment of the polynomial constants
 * a, b, c and d in GraphingPanel.
 * Loaded into south section of content pane in main method.
 */
class GraphingInput extends JPanel
{
    GraphingPanel graphingPanel;
 
    public GraphingInput(GraphingPanel gp)
    {
        graphingPanel = gp;
        final JSpinner
            aSpinner = createSpinner(),
            bSpinner = createSpinner(),
            cSpinner = createSpinner(),
            dSpinner = createSpinner();
        ChangeListener l = new ChangeListener()
        {
            int id;
 
            public void stateChanged(ChangeEvent e)
            {
                JSpinner spinner = (JSpinner)e.getSource();
                double value = ((Double)spinner.getValue()).doubleValue();
                if(spinner == aSpinner)
                    id = 0;
                if(spinner == bSpinner)
                    id = 1;
                if(spinner == cSpinner)
                    id = 2;
                if(spinner == dSpinner)
                    id = 3;
                graphingPanel.setConstant(value, id);
            }
        };
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.insets = new Insets(2,2,2,2);
        addComponents(new JLabel("a"), aSpinner, gbc, l);
        addComponents(new JLabel("b"), bSpinner, gbc, l);
        addComponents(new JLabel("c"), cSpinner, gbc, l);
        addComponents(new JLabel("d"), dSpinner, gbc, l);
    }
 
    private JSpinner createSpinner()
    {
        SpinnerNumberModel model = new SpinnerNumberModel(0.5, -1.0, 1.0, 0.01);
        JSpinner spinner = new JSpinner(model);
        spinner.setPreferredSize(new Dimension(60, spinner.getPreferredSize().height));
        return spinner;
    }
 
    private void addComponents(JLabel label, JSpinner s, GridBagConstraints gbc,
                               ChangeListener l)
    {
        gbc.anchor = gbc.EAST;
        add(label, gbc);
        gbc.anchor = gbc.WEST;
        add(s, gbc);
        s.addChangeListener(l);
    }
}

[Nicole Tan]

mm.. i can't seem to run this program.. it can't read the class file jspinner? says can't resolve symbol?

[Craig Wood]

JSpinner is a Swing component introduced in SDK1.4. If you are using an older sdk/jre they won't work.

[Nicole Tan]

cool, that's what i needed. ok... i got the graph part sorted out, but there's just this small problem.... i need to display a polynomial eqn line for each generation, how do i destroy the line for the generation b4? and since my program will run for many generation, how do i display the lines on the graph one by one without having all at one go? it seems that my program will keep running and running until it stops, then only the lines(in this case all the lines) are displayed.

[Craig Wood]

The last part of your question confuses me. Let's see what you do with this...

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.text.*;
import javax.swing.*;
import javax.swing.event.*;
 
public class Graphing1Test
{
    public static void main(String[]args)
    {
        Graphing1Panel gp = new Graphing1Panel();
        Graphing1Selection selection = new Graphing1Selection(gp);
        Graphing1Input input = new Graphing1Input(gp);
        JFrame f = new JFrame("Graphing1 Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(selection, "North");
        f.getContentPane().add(gp);
        f.getContentPane().add(input, "South");
        f.setSize(500,500);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
/**
 * Draws the polynomial when the draw button is pressed in Graphing1Input.
 * Loaded into the center section of the content pane in main method.
 * References in Graphing1Selection and Graphing1Input allow adjustments
 * to be made in polynomial constants a, b, c and d and in polynomial
 * term selection booleans showCube, showSquare, showLinear and showConstant.
 */
class Graphing1Panel extends JPanel
{
    final int PAD = 15;
    NumberFormat nf;
    final int
        A = 0,
        B = 1,
        C = 2,
        D = 3;
    boolean showCube, showSquare, showLinear, showConstant;
    double a, b, c, d;
    boolean showLine;
 
    public Graphing1Panel()
    {
        showCube = showSquare = showLinear = showConstant = true;
        a = b = c = d = 0.5;
        showLine = false;
        nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(2);
        nf.setGroupingUsed(false);
        setBackground(Color.white);
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        // ordinate
        g2.draw(new Line2D.Double(w/2, PAD, w/2, h - PAD));
        float yInc = (h - 2*PAD)/50f;
        float x1 = w/2;
        float y1 = PAD;
        for(int i = 0; i <= 50; i++)
        {
            if(i % 5 == 0)
            {
                g2.draw(new Line2D.Double(x1 - 2, y1, x1 + 2, y1));
                if(i != 25)
                    g2.drawString(String.valueOf(5 - i/5), x1 - 15, y1 + 5);
            }
            else
                g2.draw(new Line2D.Double(x1 - 1, y1, x1, y1));
            y1 += yInc;
        }
        // abcissa
        g2.draw(new Line2D.Double(PAD, h/2, w - PAD, h/2));
        float xInc = (w - 2*PAD)/50f;
        x1 = PAD;
        y1 = h/2;
        for(int i = 0; i <= 50; i++)
        {
            if(i % 5 == 0)
            {
                g2.draw(new Line2D.Double(x1, y1 - 2, x1, y1 + 2));
                if(i != 25)
                    g2.drawString(String.valueOf(i/5 - 5), x1 - 3, y1 + 15);
            }
            else
                g2.draw(new Line2D.Double(x1, y1, x1, y1 + 1));
            x1 += xInc;
        }
        // polynomial
        g2.setPaint(Color.red);
        double cube, square, linear, constant, y;
        double yLast = 0;
        double x = PAD;
        if(showLine)
        {
            for(int i = -25; i <= 25; i++)
            {
                cube = square = linear = constant = 0;
                if(showCube)
                    cube = a * Math.pow(i/5f, 3) * (h/2 - PAD)/5;
                if(showSquare)
                    square = b * Math.pow(i/5f, 2) * (h/2 - PAD)/5;
                if(showLinear)
                    linear = c * i * (h/2 - PAD)/25;
                if(showConstant)
                    constant = d * (h/2 - PAD);
                y = h/2 - (cube + square + linear + constant);
                    /*
                if(i == 10)
                {
                    System.out.println("y = " + nf.format(y) + "\n" +
                                       "cube = " + nf.format(cube) + "\n" +
                                        nf.format(cube*5/(h/2 - PAD)));
                                      // "square = " + nf.format(square) + "\n" +
                                      // "linear = " + nf.format(linear) + "\n" +
                                      // "constant = " + constant);
                    g2.fill(new Ellipse2D.Double(x - 2, y - 2, 4, 4)); 
                }
                    */
                //g2.fill(new Ellipse2D.Double(x - 2, y - 2, 4, 4));   // marker
                if(i > -25)                                            // no line on
                    g2.draw(new Line2D.Double(x - xInc, yLast, x, y)); // first pass
                x += xInc;
                yLast = y;
            }
        }
    }
 
    public void setSelector(boolean isVisible, int id)
    {
        switch(id)
        {
            case A:
                showCube = isVisible;
                break;
            case B:
                showSquare = isVisible;
                break;
            case C:
                showLinear = isVisible;
                break;
            case D:
                showConstant = isVisible;
        }
        repaint();
    }
 
    public void setConstant(double update, int id)
    {
        switch(id)
        {
            case A:
                a = update;
                break;
            case B:
                b = update;
                break;
            case C:
                c = update;
                break;
            case D:
                d = update;
        }
        repaint();
    }
 
    public void setDrawState(boolean b)
    {
        showLine = b;
        repaint();
    }
}
 
/**
 * JRadioButtons allow inclusion/exclusion of the polynomial terms by
 * setting the showCube, showSquare, showLinear and showConstant
 * booleans in Graphing1Panel.
 * Loaded into the north section of the content pane in main method.
 */
class Graphing1Selection extends JPanel
{
    Graphing1Panel graphingPanel;
 
    public Graphing1Selection(Graphing1Panel gp)
    {
        graphingPanel = gp;
        final JRadioButton
            aButton = new JRadioButton("<html><font size=5>x�</font></html>"),
            bButton = new JRadioButton("<html><font size=5>x�</font></html>"),
            cButton = new JRadioButton("<html><font size=5>x</font></html>"),
            dButton = new JRadioButton();
        ItemListener l = new ItemListener()
        {
            int id;
 
            public void itemStateChanged(ItemEvent e)
            {
                JRadioButton button = (JRadioButton)e.getSource();
                if(button == aButton)
                    id = 0;
                if(button == bButton)
                    id = 1;
                if(button == cButton)
                    id = 2;
                if(button == dButton)
                    id = 3;
                graphingPanel.setSelector(button.isSelected(), id);
            }
        };
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.insets = new Insets(0,2,0,2);
        addComponents(new JLabel("a"), aButton, gbc, l);
        addComponents(new JLabel("b"), bButton, gbc, l);
        addComponents(new JLabel("c"), cButton, gbc, l);
        addComponents(new JLabel("d"), dButton, gbc, l);
    }
 
    private void addComponents(JLabel label, JRadioButton b, GridBagConstraints gbc,
                               ItemListener l)
    {
        gbc.anchor = gbc.EAST;
        add(label,gbc);
        gbc.anchor = gbc.WEST;
        add(b, gbc);
        if(!label.getText().equals("d"))
        {
            gbc.anchor = gbc.CENTER;
            add(new JLabel("+"), gbc);
        }
        b.setSelected(true);
        b.addItemListener(l);
    }
}
 
/**
 * JSpinners allow adjustment of the polynomial constants
 * a, b, c and d in Graphing1Panel.
 * JButtons allow current polynomial to be drawn or not by
 * toggeling the showLine boolean in Graphing1Panel; 
 * Loaded into south section of content pane in main method.
 */
class Graphing1Input extends JPanel
{
    Graphing1Panel graphingPanel;
 
    public Graphing1Input(Graphing1Panel gp)
    {
        graphingPanel = gp;
        final JSpinner
            aSpinner = createSpinner(),
            bSpinner = createSpinner(),
            cSpinner = createSpinner(),
            dSpinner = createSpinner();
        ChangeListener cl = new ChangeListener()
        {
            int id;
 
            public void stateChanged(ChangeEvent e)
            {
                JSpinner spinner = (JSpinner)e.getSource();
                double value = ((Double)spinner.getValue()).doubleValue();
                if(spinner == aSpinner)
                    id = 0;
                if(spinner == bSpinner)
                    id = 1;
                if(spinner == cSpinner)
                    id = 2;
                if(spinner == dSpinner)
                    id = 3;
                graphingPanel.setConstant(value, id);
            }
        };
        final JButton
            drawButton = new JButton("draw"),
            eraseButton = new JButton("erase");
        ActionListener al = new ActionListener()
        {
            boolean flag;
 
            public void actionPerformed(ActionEvent e)
            {
                JButton button = (JButton)e.getSource();
                if(button == drawButton)
                    flag = true;
                if(button == eraseButton)
                    flag = false;
                graphingPanel.setDrawState(flag);
            }
        };
        drawButton.addActionListener(al);
        eraseButton.addActionListener(al);
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.insets = new Insets(2,2,2,2);
        addComponents(new JLabel("a"), aSpinner, gbc, cl);
        addComponents(new JLabel("b"), bSpinner, gbc, cl);
        addComponents(new JLabel("c"), cSpinner, gbc, cl);
        addComponents(new JLabel("d"), dSpinner, gbc, cl);
        gbc.anchor = gbc.CENTER;
        gbc.gridy = 1;
        gbc.gridwidth = 4;
        add(drawButton, gbc);
        add(eraseButton, gbc);
    }
 
    private JSpinner createSpinner()
    {
        SpinnerNumberModel model = new SpinnerNumberModel(0.5, -1.0, 1.0, 0.01);
        JSpinner spinner = new JSpinner(model);
        spinner.setPreferredSize(new Dimension(60, spinner.getPreferredSize().height));
        return spinner;
    }
 
    private void addComponents(JLabel label, JSpinner s, GridBagConstraints gbc,
                               ChangeListener l)
    {
        gbc.anchor = gbc.EAST;
        add(label, gbc);
        gbc.anchor = gbc.WEST;
        add(s, gbc);
        s.addChangeListener(l);
    }
}

[Nicole Tan]

i cut out most of the spinner and selection coding as i only need the graph..
here.. i'll explain waht i'm doing, i writing genetic algorithm to fit a curve, u do know what GA is right? well.. just in case, genetic algorithm works in a way that it will produce a whole set of random equations(by random generating sets of coefficients), called the population. then this population of coefficient sets will go through some operations... each time it goes through these operation, a new population will be form from the old one.. so i will have new lines everytime... going through the operations once is call one generation... so there will be tons of generations before the lines evolve themselves into better ones..
what i want is, for each generation, i want to get the best fitted line to display on the screen... but everytime i run the program... it keep evolving the population(which keeps the pc busy) and dun have time to display the graphs. it will only show the graph but no lines are produced as the algorithm is working too fast and repaiting is too slow.
this is what's left of the code, and i called the setConstant() when one generation is done in the algorithm
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.text.*;
import javax.swing.*;
import javax.swing.event.*;

/**
*
* @author TAN
*/
class Graph extends JPanel
{
final int PAD = 15;
NumberFormat nf;
double[] no = new double[4];
double a, b, c, d;
public Graph()
{

a = 0;
b = 0;
c = 0;
d = 0;
nf = NumberFormat.getNumberInstance();
nf.setMaximumFractionDigits(2);
nf.setGroupingUsed(false);
setBackground(Color.white);
}
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
int w = getWidth();
int h = getHeight();
// ordinate
g2.draw(new Line2D.Double(w/2, PAD, w/2, h - PAD));
float yInc = (h - 2*PAD)/50f;
float x1 = w/2;
float y1 = PAD;
for(int i = 0; i <= 50; i++)
{
if(i % 5 == 0)
{
g2.draw(new Line2D.Double(x1 - 2, y1, x1 + 2, y1));
if(i != 25)
g2.drawString(String.valueOf(5 - i/5), x1 - 15, y1 + 5);
}
else
g2.draw(new Line2D.Double(x1 - 1, y1, x1, y1));
y1 += yInc;
}
// abcissa
g2.draw(new Line2D.Double(PAD, h/2, w - PAD, h/2));
float xInc = (w - 2*PAD)/50f;
x1 = PAD;
y1 = h/2;
for(int i = 0; i <= 50; i++)
{
if(i % 5 == 0)
{
g2.draw(new Line2D.Double(x1, y1 - 2, x1, y1 + 2));
if(i != 25)
g2.drawString(String.valueOf(i/5 - 5), x1 - 3, y1 + 15);
}
else
g2.draw(new Line2D.Double(x1, y1, x1, y1 + 1));
x1 += xInc;
}



// polynomial
g2.setPaint(Color.red);
double cube, square, linear, constant, y;
double yLast = 0;
double x = PAD;
for(int i = -25; i <= 25; i++)
{
cube = square = linear = constant = 0;

cube = a * Math.pow(i/5f, 3) * (h/2 - PAD)/5;

square = b * Math.pow(i/5f, 2) * (h/2 - PAD)/5;

linear = c * i * (h/2 - PAD)/25;

constant = d * (h/2 - PAD);
y = h/2 - (cube + square + linear + constant);
if(i > -25) // no line on
g2.draw(new Line2D.Double(x - xInc, yLast, x, y)); // first pass
x += xInc;
yLast = y;
}

}

public void setConstant(double[] coe)
{
no = coe;
a = no[0];
b = no[1];
c = no[2];
d = no[3];
repaint();
}
}