MATLAB / Octave-网格图问题

Question

I am trying to mesh the following function in Octave:

  function C = istep(x)
      A = x < 0.75
      B = x > 0.25
      C = A & B
  endfunction

  D = rand(10);
  mesh(istep(D));

using 10x10 (random) matrix as an input. The mesh function however fails and fires

invalid value for array property "zdata"

Note: Meshing D itself works fine. The function istep also returns 10x10 "matrix" with expected values. I suspect the error lies in the fact that the internal format of the output is not treated as a matrix, but rather as a data "array" or something more abstract. I am not sure how to change it however.

Also, multiplying the output by eye(size(D)) solves the issue and allows to plot the matrix (i suspect it casts the output to matrix automatically). I do not find this very elegant though and would like to avoid it if possible.

Edit: spy() works fine directly on the output, without need of multiplication by eye()

Question: What shall I change in the code so I am able to plot the matrix istep(D)?

Answer 1

The output of your function returns logical values. So just do the following:

  mesh(double(istep(D)));