Re: Gridded2D question

• To: Cuong T Chau <Chau_Cuong_T@xxxxxxx>
• Subject: Re: Gridded2D question
• From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
• Date: Mon, 5 Jun 2000 16:31:30 -0500 (CDT)

Hi Cuong Chau,

> My apologies if this was not a recommended practice to ask question regarding
>  the usage of VISAD. Firstable let me thank you and your colleagues to provide
>  such a useful tool. I was looking for some sort of utility to plot a 3D curve
>  and was ecstatic to find your tool. I have a very simple plotting problem but
>  have spent about a week going through various VISAD tutorial and samples but
>  still couldn't find an anwser for it. Basically, I would like to produce a
>  plot that represent this relationship (x,y) -> z. The x axis in my case will
>  be an 5 element array and 10 elements for the y axis. My question is how do I
>  represent them using the Gridded2DSet. In one of the samples that shipped 
> with
>  VISAD, somebody gave the following instruction:
> 
>       double[][] samples = new double[dim][nrs];
>       .......
>       set = new Gridded2DDoubleSet(xy, samples, size, size);
> nrs in my case would be 5 * 10 = 50
> dim would be 2
> I don't know what size should it be in this case....
> 
> I only a total of 15 sample points (both x and y) so I don't know where I 
> would
>  go to find other sample points that are needed for
> VISAD. Any answer to this question is greatly appreciated.

The Gridded2DDoubleSet constructor call is:

  Gridded2DDoubleSet(MathType type, double[][] samples,
                     int lengthX, int lengthY)

In your case lengthX = 5 and lengthY = 10.  If your data are
evenly spaced in x and y, then you could use the Linear2DSet
constructor instead, called with:

  Linear2DSet(MathType type, double first1, double last1, int length1,
                             double first2, double last2, int length2)

where length1 = 5 and the 5 X points are evenly spaced between
first1 and last1, and length2 = 10 and the 10 Y points are
evenly spaced between first2 and last2.

If your data are not evenly spaced, then you must use
Gridded2DSet (or Gridded2DDoubleSet if you need double
precision for X and Y values) and you'd fill the samples
array in the constructor like this:

  int k = 0;
  for (iy=0; iy<10; iy++) {
    for (ix=0; ix<5; ix++) {
      samples[0][k] = X value of point at (ix, iy)
      samples[1][k] = Y value of point at (ix, iy)
      k++;
    }
  }

Please let us know if this is not clear.

Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • Gridded2D question
    • From: Cuong T Chau