[Octave-bug-tracker] [bug #57323] Matlab griddata includes both Octave's griddata and griddata3. Octave's related griddata errors also misleading

[Nicholas Jankowski]

URL:
  <https://savannah.gnu.org/bugs/?57323>

                 Summary: Matlab griddata includes both Octave's griddata and
griddata3. Octave's related griddata errors also misleading
                 Project: GNU Octave
            Submitted by: nrjank
            Submitted on: Fri 29 Nov 2019 03:03:38 AM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: None
             Assigned to: None
         Originator Name: Nicholas Jankowski
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 5.1.0
        Operating System: Microsoft Windows

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Details:

while trying to run an example from the Matlab help, I got an odd error from
Octave.

here's the example:


       xyz = -1 + 2*gallery('uniformdata',[5000 3],0);
       x = xyz(:,1); y = xyz(:,2); z = xyz(:,3);
       v = x.^2 + y.^2 + z.^2;
       d = -0.8:0.05:0.8;
       [xq,yq,zq] = meshgrid(d,d,0);
       vq = griddata(x,y,z,v,xq,yq,zq);
       surf(xq,yq,vq);


it should produce the image in the attached examplefig.png file.

The error received from octave running this same example was:  

>> vq = griddata(x,y,z,v,xq,yq,zq);
error: griddata: XI and YI must be vectors or matrices of same size
error: called from
    griddata at line 76 column 5


an interesting and unhelpful error because:

>> size(xq), size(yq)
ans =

   33   33

ans =

   33   33


I then noticed that Octave' griddata only takes:
ZI = griddata (X, Y, Z, XI, YI, METHOD)

and has a griddata3 function that takes:
VI = griddata3 (X, Y, Z, V, XI, YI, ZI, METHOD, OPTIONS)

according to the matlab help for griddata, it accepts optionally accepts the
inputs taken by griddata3, except it does not recognize 'options' to be passed
to the internal triangulation function.

seems compatibility could maybe be achieved by extending griddata with a
wrapper to call griddata three depending on input count/type.  Without
stepping through it, I'm not sure what triggered the misleading error message
regarding xi yi sizes not matching. 

(note that the example runs without error on Octave by changing the griddata
call to griddata3)





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File Attachments:


-------------------------------------------------------
Date: Fri 29 Nov 2019 03:03:38 AM UTC  Name: examplefig.png  Size: 69KiB   By:
nrjank

<http://savannah.gnu.org/bugs/download.php?file_id=47943>

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