[Octave-bug-tracker] [bug #56849] contour documentation wrong

[Muhali]

URL:
  <https://savannah.gnu.org/bugs/?56849>

                 Summary: contour documentation wrong
                 Project: GNU Octave
            Submitted by: muhali
            Submitted on: Mon 02 Sep 2019 08:40:52 AM PDT
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Documentation
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 5.1.0
        Operating System: GNU/Linux

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Details:

The help text for the contour function


Example:

          x = 0:2;
          y = x;
          z = x' * y;
          contour (x, y, z, 2:3)


is misleading, because one is made to believe that one can simply replace x by
e.g. 0:0.5:2 to run the same example. But that throws the error

error: __contour__: size of X must match number of columns in Z
error: called from
    __contour__ at line 88 column 9
    contour at line 74 column 18

This is caused by the definition of z, and can be avoided by letting z = y' *
x. Moreover, a non-square matrix for z clarifies things, so I recommend a help
text such as


Example:

          x = 0:3;
          y = x;
          z = y' * x;
          contour (x, y, z, 2:3)






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