Program Anomaly

[Milaffyd]

I have a program that makes use of an extended Vector. This vector stores datapoint objects, each of which contain two double type values: an x and a y. One added function to the Vector allows it to scan itself for x and y maxes, and x and y mins. For some odd reason, it is failing to do this properly and ends up storing values that are not the min nor the max in the data set. I have included the code for the scan. Any takers?
public void dataStats() {
xmax = ((datapoint) this.firstElement()).getx();
xmin = ((datapoint) this.firstElement()).getx();
ymax = ((datapoint) this.firstElement()).gety();
ymin = ((datapoint) this.firstElement()).gety();

Enumeration scan = this.elements();

while (scan.hasMoreElements()) {
datapoint processxy = (datapoint)scan.nextElement();

double y = processxy.gety();
double x = processxy.getx();
xmax = Math.max(x, xmax);
xmin = Math.min(x, xmin);
ymax = Math.max(y, ymax);
ymin = Math.min(y, ymin);
}
}

[Manfred Leonhardt]

Hi Eric,
I don't think you need to use the enum stuff. Just get the elements the usual way. Look at the following example that works great.

import java.util.*;
class datapoint 
{
  private double x;
  private double y;
  public datapoint( double x, double y )
  {
    this.x = x;
    this.y = y;
  }
  public double getx()
  {
    return( x );
  }
  public double gety()
  {
    return( y );
  }
  public void setx( double x )
  {
    this.x = x;
  }
  public void sety( double y )
  {
    this.y = y;
  }
  public String toString()
  {
    StringBuffer sb = new StringBuffer();
    sb.append( x );
    sb.append( ", " );
    sb.append( y );
    return( sb.toString() );
  }
}
public class DataPointVector extends Vector
{
  public void dataStats()
  {
    double xmax = ((datapoint)elementAt( 0 )).getx();
    double xmin = ((datapoint)elementAt( 0 )).getx();
    double ymax = ((datapoint)elementAt( 0 )).gety();
    double ymin = ((datapoint)elementAt( 0 )).gety();
    for( int i = 1; i < size(); ++i )
    {
      double x = ((datapoint)elementAt( i )).getx();
      xmax = Math.max(x, xmax);
      xmin = Math.min(x, xmin);
      double y = ((datapoint)elementAt( i )).gety();
      ymax = Math.max(y, ymax);
      ymin = Math.min(y, ymin);
    }
    System.out.println( "Data Stats results:" );
    System.out.println( "X: " + xmin + ", " + xmax );
    System.out.println( "Y: " + ymin + ", " + ymax );
  }
  public static void main(String[] args) 
  {
    DataPointVector dpv = new DataPointVector();
    for( int i = 1; i < 11; ++i )
    {
      datapoint dp = new datapoint( i * 100. * Math.random(), 
                                    i * 100. * Math.random() );
      dpv.addElement( dp );
    }
    System.out.println( "Vector:" );
    for( int j = 0; j < dpv.size(); ++j )
    {
      System.out.println( (datapoint)dpv.elementAt( j ) );
    }
    dpv.dataStats();
  }
}

Regards,
Manfred.

[Milaffyd]

Thanks, Manfred.
I tried implementing the good old-fashioned index search via the for loop. The applet still fails to acknowledge the proper maxes and mins. If anything, it seems worse since it's selected a value much less than before for a max. Could it be that some sort of memory error occurring?
http://pubweb.nwu.edu/~eyy830/JavaDev/qrs/qrs.htm
This site is where I post my running applets. Each applet relies on data from its predecessor and performs calculations to get the results you'll see. Hence, why I wonder if it's a memory error from passing vectors repetitively. You'll notice the error if you examine the very last applet panel with a time range between 0 and 1 second. That applet is the only place where I've seen the mistake.