(octave.info)Test Plotting Functions

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15.2.11 Test Plotting Functions
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The functions ‘sombrero’ and ‘peaks’ provide a way to check that
plotting is working.  Typing either ‘sombrero’ or ‘peaks’ at the Octave
prompt should display a three-dimensional plot.

 -- : sombrero ()
 -- : sombrero (N)
 -- : Z = sombrero (...)
 -- : [X, Y, Z] = sombrero (...)
     Plot the familiar 3-D sombrero function.

     The function plotted is

          z = sin (sqrt (x^2 + y^2)) / (sqrt (x^2 + y^2))

     Called without a return argument, ‘sombrero’ plots the surface of
     the above function over the meshgrid [-8,8] using ‘surf’.

     If N is a scalar the plot is made with N grid lines.  The default
     value for N is 41.

     When called with output arguments, return the data for the function
     evaluated over the meshgrid.  This can subsequently be plotted with
     ‘surf (X, Y, Z)’.

     See also: Note: peaks, Note: meshgrid,
     Note: mesh, Note: surf.

 -- : peaks ()
 -- : peaks (N)
 -- : peaks (X, Y)
 -- : Z = peaks (...)
 -- : [X, Y, Z] = peaks (...)
     Plot a function with lots of local maxima and minima.

     The function has the form

     f(x,y) = 3*(1-x)^2*exp(-x^2 - (y+1)^2) ...
              - 10*(x/5 - x^3 - y^5)*exp(-x^2-y^2) ...
              - 1/3*exp(-(x+1)^2 - y^2)

     Called without a return argument, ‘peaks’ plots the surface of the
     above function using ‘surf’.

     If N is a scalar, ‘peaks’ plots the value of the above function on
     an N-by-N mesh over the range [-3,3].  The default value for N is
     49.

     If N is a vector, then it represents the grid values over which to
     calculate the function.  If X and Y are specified then the function
     value is calculated over the specified grid of vertices.

     When called with output arguments, return the data for the function
     evaluated over the meshgrid.  This can subsequently be plotted with
     ‘surf (X, Y, Z)’.

     See also: Note: sombrero, *note meshgrid:
     XREFmeshgrid, Note: mesh, Note: surf.