[Fwd: Re: 2 questions about visaAD]

• To: visad-list@xxxxxxxxxxxxx
• Subject: [Fwd: Re: 2 questions about visaAD]
• From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
• Date: Mon, 13 Aug 2001 16:10:56 -0600

Forgot to cc: the list

-------- Original Message --------
Subject: Re: 2 questions about visaAD
Date: Mon, 13 Aug 2001 15:59:11 -0600
From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
Organization: Unidata/UCAR
To: Chen Zhang <CZhang@xxxxxxxxxxxxxxx>
References: <AD41FD390AC1D111BF1E00805F6FE65B0582C7E8@xxxxxxxxxxxxxxxxx>

Hi Chen Zang-

There are no methods in AxisScale for doing this.  It is currently way
down on the list of things to do, so won't happen any time soon.
However, there is usually more than one way to skin a cat.  You could
create a UnionSet of Gridded2DSets with manifold dimension 1, where each
Gridded2DSet would define the endpoints of the lines running from one
end of the graph to the other.  Then you would create a DataReference,
add the UnionSet to the reference and then add the reference to the
display.  So, if your RealTypes were XAxis and YAxis and you wanted
lines horizontally along the display (up the YAxis every N values), you
could do something like:

   double[] xrange = xScalarMap.getRange();
   float ymin = (float) yScalarMap.getRange()[0];
   RealType xy = new RealType(RealType.XAxis, RealType.YAxis);
   Gridded2DSet[] lineSets = new Gridded2DSet[numLines];
   for (int i = 0; i < numLines, i++) {
      float[][] points = new float[2][2];  // 2 xy points for a line
      float yValue = (float) yrange[0] + i*N  // y value for this line
      float[0][0] = (float) xrange[0];  // X value at 1st point (min X)
      float[1][0] = yValue;             // Y value at 1st point
      float[0][1] = (float) xrange[1];  // X value at 2nd point (max X)
      float[1][1] = yValue;             // Y value at 2nd point
      lineSets[i] = new Gridded2DSet(xy, points);
   }
   UnionSet lines = new UnionSet(xy, lineSets, 2);

(I haven't checked the code, but you should get the idea).  You
could do a similar thing for the Y values.  I do this to draw lat/lon
lines on a map.

You could also use an array of ConstantMaps when you add in the
reference to make the lines a specific color.

Don Murray
   

Chen Zhang wrote:
> 
> thank you for your prompt reply.
> 
> is it possible to draw grid lines in a 2D graph for Y axis?  now, i am able
> to set customized scale for Y axis.  i need to draw lines across the graph
> to make reading easier.
> 
> thanx.
> cz

*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************