Problems with precision & ScalarMap

• To: VisAD List <visad-list@xxxxxxxxxxxxx>
• Subject: Problems with precision & ScalarMap
• From: Timo Thomas <tthomas@xxxxxxxxxxxxxxxxxxxxxxxx>
• Date: Wed, 23 May 2001 13:27:23 +0200

Hi list,

the attached slightly modified P2_01 example doesn't work. There seems to be 
a problem with big data values. If I don't set the range of heightMap 
explicitly, the ScalarMap isn't initialized to the correct min/max data 
values (it rounds them somehow). If I set it, it takes minutes before a 
window is shown and there's only a point shown instead of a line.   
Maybe there's an unintended double to float conversion happening internally?

Timo
-- 
__.__________
 |lmo |homas

/*
VisAD Tutorial
Copyright (C) 2000 Ugo Taddei
*/

// Import needed classes

import visad.*;
import visad.java2d.DisplayImplJ2D;
import java.rmi.RemoteException;
import java.awt.*;
import javax.swing.*;

/**
  Enhanced version of program P1_01. 
  Draw function height = 45 - 5 * time^2
  Rename RealTypes and attach units to them.
  Draw scales on display to show the RealTypes names.
  Run program with java P2_01 
 */


public class P2_01{

  // Declare variables
  // The quantities to be displayed in x- and y-axes
  
  private RealType time, height;

  
  // The function height = f( time ), represented by ( time -> height )
  
  private FunctionType func_t_h; 


  // Our Data values for time are represented by the set

  private Set time_set;

   
  // The Data class FlatField, which will hold time and height data.
  // time data are implicitely given by the Set time_set
   
  private FlatField h_vals_ff;  
 
  
  // The DataReference from the data to display
  
  private DataReferenceImpl data_ref;


  // The 2D display, and its the maps
  
  private DisplayImpl display;
  private ScalarMap timeMap, heightMap;
  
  // The conctructor for our example class
  
  public P2_01 (String []args)
    throws RemoteException, VisADException {

    // Create the quantities
    // time and height are measured in SI seconds and SI meters, respectively
    // Use RealType(String name, Unit u,  Set set), set is null
    
    time = new RealType("time", SI.second, null);
    height = new RealType("height", SI.meter, null);
      
  
    // Create a FunctionType, that is the class which represents the function 
    // height = f(time), that is the MathType ( time -> height )
    // Use FunctionType(MathType domain, MathType range) 
   
    func_t_h = new FunctionType(time, height);
   
    
    // These are our actual data values
    
    // Create the time_set, with 5 integer values, ranging from 0 to 4.
    // That means, that there should be 5 values for height.
    // Use Integer1DSet(MathType type, int length) 
        
    time_set = new Integer1DSet(time, 5);
    
    // ...the height values
    
    float[][] h_vals = new float[][]{{0.0f, 33.75f, 45.0f, 33.75f, 0.0f,} };
    double[][] dh_vals = new double[][]{{917855104, 917855104.25, 917855104.5, 
917855104.75, 917855105.0,} };
         //    double[][] dh_vals2 = new double[][]{{917855104-dh_vals[0][0], 
917855104.25-dh_vals[0][0], 917855104.5-dh_vals[0][0], 
917855104.75-dh_vals[0][0], 917855105.0-dh_vals[0][0],} };
  
         for (int i=0; i < dh_vals[0].length; i++)
                  System.out.println(dh_vals[0][i]);
         
         //for (int i=0; i < dh_vals2[0].length; i++)
         //               System.out.println(dh_vals2[0][i]);
    // Create a FlatField, that is the class for the samples 
    // Use FlatField(FunctionType type, Set domain_set)
    
    h_vals_ff = new FlatField( func_t_h, time_set);
    
    
    // and put the height values above in it
     
    h_vals_ff.setSamples( dh_vals ); 
     
     
    // Create Display and its maps
    
    // A 2D display
    
    display = new DisplayImplJ2D("display1");
    
    // Get display's graphics mode control and draw scales
    
    GraphicsModeControl dispGMC = (GraphicsModeControl) 
display.getGraphicsModeControl();
    dispGMC.setScaleEnable(true);    
    
    
    // Create the ScalarMaps: quantity time is to be displayed along XAxis
    // and height along YAxis
    // Use ScalarMap(ScalarType scalar, DisplayRealType display_scalar) 
                    
    timeMap = new ScalarMap( time, Display.XAxis );
    heightMap = new ScalarMap( height, Display.YAxis );
         System.out.println("" + dh_vals[0][0] + ", " + 
dh_vals[0][dh_vals[0].length-1]);
         heightMap.setRange(dh_vals[0][0], dh_vals[0][dh_vals[0].length-1]);
         //    heightMap.setRange(0, 2) ;
         
    
    // Add maps to display
    
    display.addMap( timeMap );
    display.addMap( heightMap );
    
    
    // Create a data reference and set the FlatField as our data 
    
    data_ref = new DataReferenceImpl("data_ref");
    
    data_ref.setData( h_vals_ff );
    
    
    // Add reference to display
    
    display.addReference( data_ref );
    
    
    // Create application window, put display into it 
  
    JFrame jframe = new JFrame("My second VisAD application");
    jframe.getContentPane().add(display.getComponent());
    
    
    // Set window size and make it visible
    
    jframe.setSize(300, 300);
    jframe.setVisible(true);
    
  }
  
  
  public static void main(String[] args)
    throws RemoteException, VisADException
  {
    new P2_01(args);
  }

} //end of Visad Tutorial Program 2_01

• Follow-Ups:
  • Re: Problems with precision & ScalarMap
    • From: Don Murray