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########################################################################
##
## Copyright (C) 1993-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {} sombrero ()
## @deftypefnx {} {} sombrero (@var{n})
## @deftypefnx {} {@var{z} =} sombrero (@dots{})
## @deftypefnx {} {[@var{x}, @var{y}, @var{z}] =} sombrero (@dots{})
## Plot the familiar 3-D sombrero function.
##
## The function plotted is
## @tex
## $$z = { \rm{sin} (\sqrt {(x^2 + y^2)}) \over \sqrt {(x^2 + y^2)} }$$
## @end tex
## @ifnottex
##
## @example
## z = sin (sqrt (x^2 + y^2)) / (sqrt (x^2 + y^2))
## @end example
##
## @end ifnottex
## Called without a return argument, @code{sombrero} plots the surface of the
## above function over the meshgrid [-8,8] using @code{surf}.
##
## If @var{n} is a scalar the plot is made with @var{n} grid lines.
## The default value for @var{n} is 41.
##
## When called with output arguments, return the data for the function
## evaluated over the meshgrid. This can subsequently be plotted with
## @code{surf (@var{x}, @var{y}, @var{z})}.
##
## @seealso{peaks, meshgrid, mesh, surf}
## @end deftypefn
function [x, y, z] = sombrero (n = 41)
if (n <= 1)
error ("sombrero: number of grid lines N must be greater than 1");
endif
[xx, yy] = meshgrid (linspace (-8, 8, n));
r = sqrt (xx.^2 + yy.^2) + eps; # eps prevents div/0 errors
zz = sin (r) ./ r;
if (nargout == 0)
surf (xx, yy, zz);
elseif (nargout == 1)
x = zz;
else
x = xx;
y = yy;
z = zz;
endif
endfunction
%!demo
%! clf;
%! colormap ("default");
%! sombrero ();
%! title ("sombrero() function");
## Test input validation
%!error sombrero (1,2,3)
%!error <N must be greater than 1> sombrero (1)
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