SimplePlotPanel.java

// SimplePlotPanel.java
//
// Rahul Simha
// Spring 2008

import java.util.*;
import java.text.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;

public class SimplePlotPanel extends JPanel {

  public static int glueSpace = 3;                    // Generic spacing between lines, text.
  public static int axisLabelFontSize = 10;           // Font size for axis labels.
  public static int tickFontSize = 8;                 // Same for tickmark labels.
  public static int legendFontSize = 16;              // Legend.
  public static int tickSize = 6;                     // Length of each tick mark.
  public static int titleFontSize = 12;               // Length of each tick mark.
  public static int pointBlobRadius = 4;              // Size of circle to mark a point.
  
  // Fonts and associated FontMetrics references:
  Font legendFont, tickFont, axisLabelFont, titleFont;
  FontMetrics tickFontMetrics, axisLabelFontMetrics, legendFontMetrics, titleFontMetrics;

  // Various box boundaries:
  // The panel:
  int panelHeight, panelWidth;
  // If an external bounding box is given:
  int bboxLeft, bboxRight, bboxTop, bboxBottom, bboxHeight, bboxWidth;
  // The inner box in which the curves are plotted:
  int plotBoxTopInset, plotBoxBottomInset, plotBoxLeftInset, plotBoxRightInset;
  int plotBoxHeight, plotBoxWidth, plotBoxLeft, plotBoxRight, plotBoxTop, plotBoxBottom;
  // The outerbox that contains the plotbox and the labels:
  int graphBoxHeight, graphBoxWidth, graphBoxLeft, graphBoxRight, graphBoxTop, graphBoxBottom;
  // The box below the outerbox that contains the legend:
  int legendBoxHeight, legendBoxWidth;
  
  int maxNumCurves;                              // Max allowable curves: for storage.
  int numCurves;                                 // Actual number of curves.
  int maxNumValues;
  SimplePlotCurve[] curves;                      // The curves themselves.

  double Xmax, Xmin, Xrange;                     // Lowest, highest, and range of X values.
  double Ymax, Ymin, Yrange;                     // Same for Y.

  int numXTicks, numYTicks;                      // Number of tick marks.
  double[] XTicks, YTicks;                       // The actual points for the ticks.
  String[] XTickLabels, YTickLabels;             // Labels.
  int XTickWidth, XTickHeight;                   // Font heights and widths.
  int YTickWidth, YTickHeight;

  String XaxisLabelString = "", YaxisLabelString = "";     // Axis labels.

  DecimalFormat Xformat, Yformat;                // Format labels/ticks.

  String titleString = "";                       // Title to appear center-top.


  // A set of colors to use.

  static Color colors[] = {Color.red, Color.blue, Color.green, Color.magenta, Color.cyan, Color.orange, Color.yellow,   
Color.pink, Color.lightGray};

  // Parameters to constructor: total number of curves. Over all curves,
  // the largest number of X values, the largest number of Y values.

  public SimplePlotPanel (int maxNumCurves, int maxNumValues)
  {
    this.setBackground (Color.white);

    // Curve data:
    this.maxNumCurves = maxNumCurves;
    this.maxNumValues = maxNumValues;
    numCurves = 0;
    curves = new SimplePlotCurve [maxNumCurves];
    for (int i=0; i<maxNumCurves; i++) {
      curves[i] = new SimplePlotCurve (maxNumValues);
    }

    // Range stuff:
    Ymax = Xmax = Double.NEGATIVE_INFINITY;
    Ymin = Xmin = Double.POSITIVE_INFINITY;
    Xrange = Yrange = 0;
    // Tick marks:
    numXTicks = numYTicks = -1;
    XTicks = new double [maxNumValues+1];
    YTicks = new double [maxNumValues+1];
    XTickLabels = new String [maxNumValues+1];
    YTickLabels = new String [maxNumValues+1];

    // Font stuff:
    legendFont = new Font ("Serif", Font.BOLD | Font.ITALIC, legendFontSize);
    axisLabelFont = new Font ("SansSerif", Font.BOLD, axisLabelFontSize);
    tickFont = new Font ("SansSerif", Font.PLAIN, tickFontSize);
    titleFont = new Font ("Serif", Font.BOLD, titleFontSize);

  }
  

  // Plot one curve only
  static JFrame frame;

  public static void makePlotFrame (Vector points, String name, int frameWidth, int frameHeight)
  {
      SimplePlotPanel panel = new SimplePlotPanel (1, points.size());
      panel.setNumXTicks (10);
      panel.setNumYTicks (10);
      int ID = panel.createNewCurve (name, Color.blue);
      panel.setXYPoints (ID, points);
      frame = new JFrame ();
      frame.setSize (frameWidth, frameHeight);
      frame.getContentPane().add (panel);
      frame.addWindowListener (new WindowAdapter () {
	      public void windowClosing (WindowEvent e) 
	      {
		  frame.dispose ();
	      }
      });
      frame.setVisible (true);
  }


  public static void makePlotFrame (Vector points)
  {
      makePlotFrame (points, "", 600, 480);
  }

  public static void makePlotFrame (ArrayList<Vector> pointSets, ArrayList<String> names, String xLabel, int frameWidth, int frameHeight)
  {
      Vector[] pointSetVector = new Vector [pointSets.size()];
      String[] nameVector = new String [names.size()];
      for (int i=0; i<pointSets.size(); i++) {
          pointSetVector[i] = pointSets.get(i);
          nameVector[i] = names.get(i);
      }
      makePlotFrame (pointSetVector, nameVector, xLabel, frameWidth, frameHeight);
  }

  public static void makePlotFrame (String title, ArrayList<Vector> pointSets, ArrayList<String> names, String xLabel, int frameWidth, int frameHeight)
  {
      // titleString = title;
      Vector[] pointSetVector = new Vector [pointSets.size()];
      String[] nameVector = new String [names.size()];
      for (int i=0; i<pointSets.size(); i++) {
          pointSetVector[i] = pointSets.get(i);
          nameVector[i] = names.get(i);
      }
      makePlotFrame (pointSetVector, nameVector, xLabel, frameWidth, frameHeight);
  }


  public static void makePlotFrame (Vector[] pointSets, String[] names, String xLabel, int frameWidth, int frameHeight)
  {
      

      // Find largest set.
      int N = pointSets[0].size();
      for (int i=1; i<pointSets.length; i++) {
	  if (N < pointSets[i].size()) {
	      N = pointSets[i].size();
	  }
      }


      SimplePlotPanel panel = new SimplePlotPanel (pointSets.length, N);
      panel.setXaxisLabel (xLabel);
      panel.setNumXTicks (10);
      panel.setNumYTicks (10);
      for (int i=0; i<pointSets.length; i++) {
	  //System.out.println ("Simple.makeNew(): i=" + i + " names[i]=" + names[i]);
	  int ID = panel.createNewCurve (names[i], colors[i % colors.length]);
	  panel.setXYPoints (ID, pointSets[i]);
      }
      frame = new JFrame ();
      frame.setSize (frameWidth, frameHeight);
      frame.getContentPane().add (panel);
      frame.addWindowListener (new WindowAdapter () {
	      public void windowClosing (WindowEvent e) 
	      {
		  frame.dispose ();
	      }
      });
      frame.setVisible (true);
  }


  /**
   * <code>paintComponent</code> overrides the <code>JPanel</code>'s
   * method of the same name.
   *
   * @param g a <code>Graphics</code> value
   */

  public void paintComponent (Graphics g)
  {
    super.paintComponent (g);

    setBounds ();

    // Now plot:
    makePlot (g);
  }

  private void setBounds ()
  {
    // Set the bounding box to be the panel:
    Dimension D = this.getSize();
    panelHeight = D.height;
    panelWidth = D.width;
    bboxLeft = bboxTop = 0;
    bboxRight = panelWidth;
    bboxBottom = panelHeight;
  }
  
  

  ////////////////////////////////////////////////////////////////////
  // For public use:

  /**
   * Call <code>setTitle</code> with the plot title to be displayed.
   *
   * @param titleString a <code>String</code> value
   */

  public void setTitle (String titleString)
  {
    this.titleString = titleString;
  }
  

  /**
   * Call <code>createNewCurve</code> each time a new curve is to be started,
   * before adding data for the curve. 
   *
   * @param legendString a <code>String</code> value
   * @return an <code>int</code> value: a curveID that is to be used later.
   */

  public int createNewCurve (String legendString, Color color)
  {
    numCurves ++;
    curves[numCurves-1].legendString = legendString;
    curves[numCurves-1].color = color;
    return numCurves-1;
  }


  /**
   * Set the X-axis label.
   *
   * @param XaxisLabelString a <code>String</code> value
   */

  public void setXaxisLabel (String XaxisLabelString)
  {
    this.XaxisLabelString = XaxisLabelString;
  }
  

  /**
   * Set the Y-axis label.
   *
   * @param YaxisLabelString a <code>String</code> value
   */

  public void setYaxisLabel (String YaxisLabelString)
  {
    this.YaxisLabelString = YaxisLabelString;
  }


  /**
   * Set the number of X-axis tick marks.
   *
   * @param numXTicks an <code>int</code> value
   */

  public void setNumXTicks (int numXTicks)
  {
    if (numXTicks <= maxNumValues) {
      this.numXTicks = numXTicks;
    }
  }
  

  /**
   * Set the number of Y-axis tick marks.
   *
   * @param numYTicks an <code>int</code> value
   */

  public void setNumYTicks (int numYTicks)
  {
    if (numYTicks <= maxNumValues) {
      this.numYTicks = numYTicks;
    }
  }
  

  public void setPointRadius (int numPixels)
  {
    if (numPixels > 0) {
      pointBlobRadius = numPixels;
    }
  }
  


  /**
   * Call <code>setXVector</code> with a set of X-values for a particular curve,
   * AFTER the curve has been created.
   * This MUST be called before the corresponding Y-values are given.
   * The Y-values can be given as a vector, or one by one to allowing
   * for incremental plotting.
   *
   * @param curveID an <code>int</code> value
   * @param X a <code>double[]</code> value
   * @exception SimPlotException if an error occurs
   */

  public void setXVector (int curveID, double[] X)
  {
    if (curveID >= maxNumCurves) {
	return;
    }

    if (X.length > maxNumValues) {
	return;
    }

    curves[curveID].setXValues (X);

    // Update range:
    double min = X[0], max = X[0];
    for (int i=0; i<X.length; i++) {
      if (X[i] < min)
        min = X[i];
      if (X[i] > max)
        max = X[i];
    }
    if (min < Xmin)
      Xmin = min;
    if (max > Xmax)
      Xmax = max;
    Xrange = Xmax - Xmin;
  }


  /**
   * Call <code>setYVector</code> to pass in a set of Y-values for a
   * a particular curve. Call this only after setting the X-values for
   * the same curve.
   *
   * @param curveID an <code>int</code> value
   * @param Y a <code>double[]</code> value
   * @exception SimPlotException if an error occurs
   */

  public void setYVector (int curveID, double[] Y)
  {
    if (curveID >= maxNumCurves) {
	return;
    }

    if (Y.length != curves[curveID].getNumXValues()) {
	return;
    }

    curves[curveID].setYValues (Y);


    // Update range:
    double min = Y[0], max = Y[0];
    for (int i=0; i<Y.length; i++) {
      if (Y[i] < min)
        min = Y[i];
      if (Y[i] > max)
        max = Y[i];
    }
    if (min < Ymin)
      Ymin = min;
    if (max > Ymax)
      Ymax = max;
    Yrange = Ymax - Ymin;
  }


  /**
   * You can call <code>addNewYValue</code> for a curve, once for each
   * Y-value for incremental plotting. In this case, the caller needs
   * to <code>repaint</code> the panel.
   *
   * @param curveID an <code>int</code> value
   * @param y a <code>double</code> value
   * @exception SimPlotException if an error occurs
   */

  public void addNewYValue (int curveID, double y)
  {
    if (curveID >= maxNumCurves) {
	return;
    }

    if (curves[curveID].getNumYValues() >= curves[curveID].getNumXValues()) {
	return;
    }

    curves[curveID].addNewYValue (y);

    // Adjust range:
    if (y < Ymin)
      Ymin = y;
    if (y > Ymax)
      Ymax = y;
    Yrange = Ymax - Ymin;
  }
  


  public void setXYPoints (int curveID, Vector points)
  {
    if (points == null)
      return;
    if (curveID >= maxNumCurves) {
	return;
    }

    int numPoints = points.size();
    if (points.size() > maxNumValues) {
	numPoints = maxNumValues;
    }

    double[] X = new double [numPoints];
    double[] Y = new double [numPoints];
    for (int i=0; i<numPoints; i++) {
      Object obj = points.get (i);
      if (! (obj instanceof Point2D.Double)) {
	  return;
      }
      Point2D.Double p = (Point2D.Double) obj;
      X[i] = p.x;
      Y[i] = p.y;
    }

    setXVector (curveID, X);
    setYVector (curveID, Y);
  }



  /**
   * Call <code>makePlot</code> to make the plotter plot on a <code>Graphics</code>
   * instance of your choice, with a specified bounding box within which to draw.
   *
   * @param g a <code>Graphics</code> value
   * @param boundingBoxTopLeftX an <code>int</code> value - the top left corner of the box (X)
   * @param boundingBoxTopLeftY an <code>int</code> value - top left Y value.
   * @param boundingBoxWidth an <code>int</code> value - width of the box.
   * @param boundingBoxHeight an <code>int</code> value - height of the box.
   */

  public void makePlot (Graphics g, int boundingBoxTopLeftX, int boundingBoxTopLeftY, 
                 int boundingBoxWidth, int boundingBoxHeight)
  {
    bboxLeft = boundingBoxTopLeftX;
    bboxRight = bboxLeft + boundingBoxWidth;
    bboxTop = boundingBoxTopLeftY;
    bboxBottom = bboxTop + boundingBoxHeight;
    makePlot (g);
  }
  




  ////////////////////////////////////////////////////////////////////
  // Drawing

  void makePlot (Graphics g)
  {
    // Compute sizes:
    computeDrawingConstants (g);

    // Draw the bounding box:
    g.setColor (Color.black);
    g.drawRect (bboxLeft, bboxTop, bboxWidth, bboxHeight);

    // Draw legend line:
    g.drawLine (bboxLeft, graphBoxBottom, bboxRight, graphBoxBottom);
    writeLegends (g);

    // Draw plot box:
    g.setColor (Color.black);
    g.drawRect (plotBoxLeft, plotBoxTop, plotBoxWidth, plotBoxHeight);

    // Write labels:
    g.setFont (axisLabelFont);
    int x = bboxLeft + glueSpace;
    int y = bboxTop + 2*glueSpace + axisLabelFontMetrics.getHeight() 
            + titleFontMetrics.getHeight();
    g.drawString (YaxisLabelString, x, y);
    x = graphBoxRight - glueSpace - axisLabelFontMetrics.stringWidth (XaxisLabelString);
    y = graphBoxBottom - glueSpace;
    g.drawString (XaxisLabelString, x, y);

    // Draw and write ticks:
    g.setFont (tickFont);
    drawTicks (g);

    // Write title.
    x = (bboxLeft + bboxRight) / 2;
    y = bboxTop + 2*glueSpace + titleFontMetrics.getHeight();
    g.setColor (Color.black);
    g.setFont (titleFont);
    g.drawString (titleString, x, y);
    
    // Plot curves:
    for (int i=0; i<numCurves; i++) {
      plotCurve (g, curves[i]);
    }
    
  }

  int dataXToPixelValue (double x)
  {
    // Take a graph coordinate and get the pixel value for drawing.
    // First, the pixel value with regular coordinates:
    int regularX = (int) Math.round (((x - Xmin) / Xrange) * plotBoxWidth);
    // Now shift:
    return regularX + bboxLeft + plotBoxLeftInset;
  }

  int dataYToPixelValue (double y)
  {
    // Take a graph coordinate and get the pixel value for drawing.
    // First, the pixel value with regular coordinates:
    int regularY = (int) Math.round (((y - Ymin) / Yrange) * plotBoxHeight);
    // Now shift:
    return bboxTop + plotBoxTopInset + (plotBoxHeight - regularY);
  }
  

  void computeDrawingConstants (Graphics g)
  {
    // Boundingbox limits:
    bboxHeight = bboxBottom - bboxTop;
    bboxWidth = bboxRight - bboxLeft;

    // Legend stuff:
    legendBoxWidth = bboxWidth;
    g.setFont (legendFont);
    legendFontMetrics = g.getFontMetrics();
    legendBoxHeight = legendFontMetrics.getHeight() * numCurves + 4*glueSpace;

    // GraphBox stuff:
    graphBoxWidth = bboxWidth;
    graphBoxHeight = bboxHeight - legendBoxHeight;
    graphBoxLeft = bboxLeft;
    graphBoxRight = graphBoxLeft + graphBoxWidth;
    graphBoxTop = bboxTop;
    graphBoxBottom = graphBoxTop + graphBoxHeight;

    // Need to do ticks next, to get tick distances:
    g.setFont (tickFont);
    tickFontMetrics = g.getFontMetrics();
    makeTicks (g);

    // plotBox stuff:
    g.setFont (titleFont);
    titleFontMetrics = g.getFontMetrics();
    int titleFontHeight = titleFontMetrics.getHeight();
    g.setFont (axisLabelFont);
    axisLabelFontMetrics = g.getFontMetrics();
    int axisLabelHeight = axisLabelFontMetrics.getHeight();
    plotBoxTopInset = 6*glueSpace + axisLabelHeight + titleFontHeight;
    plotBoxBottomInset = 4*glueSpace + tickFontMetrics.getHeight() + axisLabelHeight;
    plotBoxRightInset = 4*glueSpace + XTickWidth + tickSize/2;
    plotBoxLeftInset = 4*glueSpace + YTickWidth + tickSize/2;
    plotBoxWidth = graphBoxWidth - (plotBoxLeftInset + plotBoxRightInset);
    plotBoxHeight = graphBoxHeight - (plotBoxTopInset + plotBoxBottomInset);
    plotBoxTop = graphBoxTop + plotBoxTopInset;
    plotBoxBottom = plotBoxTop + plotBoxHeight;
    plotBoxLeft = graphBoxLeft + plotBoxLeftInset;
    plotBoxRight = plotBoxLeft + plotBoxWidth;
  }


  void makeTicks (Graphics g)
  {
    if ( (numXTicks < 0) || (numYTicks < 0) )
      numXTicks = numYTicks = estimateNumXTicks (g);
    createFormats();
    makeXTicks ();
    makeYTicks ();
  }
  

  void drawTicks (Graphics g)
  {
    for (int i=0; i<numXTicks; i++)
      drawXTick (g, XTicks[i], XTickLabels[i]);
    for (int i=0; i<numYTicks; i++)
      drawYTick (g, YTicks[i], YTickLabels[i]);
  }
  

  int estimateNumXTicks (Graphics g)
  {
    // Do this by seeing how many ticks for Xmax will fit.
    int width = tickFontMetrics.stringWidth ("" + Xmax);
    int n = graphBoxWidth / (width + 2*glueSpace);
    // System.out.println ("estimateNumXTicks(): Xmax=" + Xmax + " w=" + width + " n=" + n);
    // Reduce by 1 to be safe.
    if (n > 4)
      n --;
    if (n > maxNumValues)
     n = maxNumValues;
    // System.out.println ("estimateNumXTicks=" + n);
    return n;
  }
  


  void makeXTicks ()
  {
    // Force an odd number of ticks:
    if (numXTicks % 2 == 0)
      numXTicks++;
    double intervalSize = Xrange / (numXTicks-1);
    XTicks[0] = Xmin;
    for (int i=1; i<=numXTicks-2; i++)
      XTicks[i] = XTicks[i-1] + intervalSize;
    XTicks[numXTicks-1] = Xmax;
    // Now for labels:
    int maxWidth = Integer.MIN_VALUE;
    for (int i=0; i<numXTicks; i++) {
      XTickLabels[i] = makeDoubleFormatX (XTicks[i]);
      int width = tickFontMetrics.stringWidth (XTickLabels[i]);
      if (width > maxWidth)
        maxWidth = width;
      // System.out.println ("makeXTicks(): i=" + i + " XTick[i]=" + XTicks[i]);
    }
    // We'll need this for writing:
    XTickWidth = maxWidth;
  }
  
  void makeYTicks ()
  {
    if (numYTicks % 2 == 0)
      numYTicks++;
    double intervalSize = Yrange / (numYTicks-1);
    YTicks[0] = Ymin;
    for (int i=1; i<=numYTicks-2; i++)
      YTicks[i] = YTicks[i-1] + intervalSize;
    YTicks[numYTicks-1] = Ymax;
    // Now for labels:
    int maxWidth = Integer.MIN_VALUE;
    for (int i=0; i<numYTicks; i++) {
      YTickLabels[i] = makeDoubleFormatY (YTicks[i]);
      int width = tickFontMetrics.stringWidth (YTickLabels[i]);
      if (width > maxWidth)
        maxWidth = width;
      // System.out.println ("makeYTicks(): i=" + i + " YTickLabels[i]=" + YTickLabels[i] + " w=" + width + " max=" + maxWidth);
    }
    YTickWidth = maxWidth;
  }


  void createFormats ()
  {
    // Based on Xmin, Xmax: 
    Xformat = makeFormat (Xmin, Xmax);
    // Based on Ymin, Ymax:
    Yformat = makeFormat (Ymin, Ymax);
  }
  

  DecimalFormat makeFormat (double low, double high)
  {
    // Find out precision required:
    String formatStr = "#.##";
    double value = low;

    if (low == 0.0) {
      // Use high, possibly.
      if ( (high == 0) || (high > 1) )
        return new DecimalFormat (formatStr);
      value = high;
    }
    // Make it positive:
    if (value < 0) value = value * (-1);
    while (value < 1) {
      value = value * 10;
      formatStr = formatStr + "#";
    }
    // System.out.println ("low=" + low + " high=" + high + " value=" + value + " formatStr=" + formatStr);
    return new DecimalFormat (formatStr);
  }
  

  String makeDoubleFormatX (double x)
  {
    String str= Xformat.format (x);
    // System.out.println ("makeX: x=" + x + " str=" + str);
    return str;
  }

  String makeDoubleFormatY (double y)
  {
    String str = Yformat.format (y);
    // System.out.println ("makeY: y=" + y + " str=" + str);
    return str;
  }

  void drawXTick (Graphics g, double x, String tickLabel)
  {
    // System.out.println ("DrawXTick: numXTicks=" + numXTicks + " x=" + x + " label=" + tickLabel);
    
    // Draw a tick at data position x.
    int xTick = dataXToPixelValue (x);
    int y = plotBoxBottom;
    g.setColor (Color.darkGray);
    g.drawLine (xTick, y+tickSize/2, xTick, y-tickSize/2);
    if (tickLabel != null) {
      // Put a label centered at xTick.
      int xLabelPos = xTick - (tickFontMetrics.stringWidth(tickLabel) / 2);
      int yLabelPos = plotBoxBottom + glueSpace 
                      + tickSize/2 + tickFontMetrics.getHeight();
      g.drawString (tickLabel, xLabelPos, yLabelPos);
    }
  }
  

  void drawYTick (Graphics g, double y, String tickLabel)
  {
    // System.out.println ("DrawYTick: numYTicks=" + numYTicks + " y=" + y + " label=" + tickLabel);

    // Draw a tick at data position y.
    int yTick = dataYToPixelValue (y);
    int x = plotBoxLeft;
    g.setColor (Color.darkGray);
    g.drawLine (x-tickSize/2, yTick, x+tickSize/2, yTick);
    if (tickLabel != null) {
      // Put a label.
      int xLabelPos = plotBoxLeft - tickSize/2 - 2*glueSpace
                      - tickFontMetrics.stringWidth(tickLabel);
      int yLabelPos = yTick + tickFontMetrics.getHeight()/2;
      g.drawString (tickLabel, xLabelPos, yLabelPos);
    }
  }


  void writeLegends (Graphics g)
  {
    for (int i=0; i<numCurves; i++) {
      // Write the legend string for curve i. First, the font.
      g.setFont (legendFont);
      // Now, the location
      int x = graphBoxLeft + 4*glueSpace;
      int legendFontHeight = g.getFontMetrics().getHeight();
      int y = graphBoxBottom + 2*glueSpace + ((i+1) * legendFontHeight);
      g.setColor (curves[i].color);
      g.drawString (curves[i].legendString, x, y);
    }
  }


  void plotCurve (Graphics g, SimplePlotCurve curve)
  {
    g.setColor (curve.color);
    int x=0, y=0, prev_x=0, prev_y=0;
    for (int i=0; i<curve.getNumValues(); i++) {
      // Plot the point X[i],Y[i].
      if (i > 0) {
        prev_x = x; prev_y = y;
      }
      x = dataXToPixelValue (curve.getX(i));
      y = dataYToPixelValue (curve.getY(i));
      g.fillOval (x-pointBlobRadius, y-pointBlobRadius, 2*pointBlobRadius, 2*pointBlobRadius);
      //** Joint the dots? Assumes data is sorted.
      if (i > 0) 
        g.drawLine (prev_x, prev_y, x, y);
    }
    
  }
  
}

class SimplePlotCurve {

  private int maxNumValues;          // Maximum number of points.
  private int numXValues;            // Actual number of points.
  private int numCurrentYValues;     // Number of Y values added so far.
  String legendString;               // String to print in legend.
  Color color;                       // Preferred color.

  private double[] X, Y;     // The points.

  public SimplePlotCurve (int maxNumValues)
  {
    X = new double [maxNumValues];
    Y = new double [maxNumValues];
    numXValues = 0;
    numCurrentYValues = 0;
  }
  
  public void setXValues (double[] X)
  {
    numXValues = 0;
    for (int i=0; i<X.length; i++) {
      numXValues++;
      this.X[numXValues-1] = X[i];
    }
  }

  public void setYValues (double[] Y)
  {
    numCurrentYValues = 0;
    for (int i=0; i<Y.length; i++) {
      numCurrentYValues ++;
      this.Y[numCurrentYValues-1] = Y[i];
    }
  }
  

  public void addNewYValue (double y)
  {
    numCurrentYValues ++;
    Y[numCurrentYValues-1] = y;
  }

  public int getNumXValues ()
  {
    return numXValues;
  }
  

  public int getNumValues ()
  {
    if (numXValues > numCurrentYValues)
      return numCurrentYValues;
    else
      return numXValues;
  }
  
  public int getNumYValues ()
  {
    return numCurrentYValues;
  }
  

  public double getX (int i)
  {
    return X[i];
  }

  public double getY (int i)
  {
    return Y[i];
  }
  
}