[Octave-bug-tracker] [bug #49886] ezplot: octave does not warn when function not vectorized -- and exhibits a wrong plot

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?49886>

                 Summary: ezplot: octave does not warn when function not
vectorized -- and exhibits a wrong plot
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Mon 19 Dec 2016 01:12:49 PM UTC
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Alain Cochard
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.3
        Operating System: GNU/Linux

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Details:

With the following (correct) syntax, the plot is OK, with both matlab
and octave:


ezsurf(@(x,y) x+y+x.^2, [-2 2])


With this incorrect syntax (the period is omitted)


ezsurf(@(x,y) x+y+x^2, [-2 2])


the plot is OK with matlab, with the warning message:


Warning: Function failed to evaluate on array inputs; vectorizing the
function may speed up its evaluation and avoid the need to loop over
array elements.
> In specgraph/private/ezplotfeval at 59
  In ezgraph3>ezeval at 623
  In ezgraph3>surfplot at 550
  In ezgraph3 at 49
  In ezsurf at 65


but it is totally wrong with octave (although not strikingly wrong at
first sight, i.e., not pure garbage), *without any warning*.

Also, if one provides a 3rd argument (number of points to be used) to
ezplot, the plot is different for different values of that argument.

I have tried versions 3.4.3, 3.8.2, 4.0.3, all with Fedora or CentOS
GNU/Linux distributions.





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