update packages

[CreaPhase.git] / octave_packages / m / plot / cylinder.m

diff --git a/octave_packages/m/plot/cylinder.m b/octave_packages/m/plot/cylinder.m
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+## Copyright (C) 2007-2012 Michael Goffioul and Kai Habel
+##
+## 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
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} cylinder
+## @deftypefnx {Function File} {} cylinder (@var{r})
+## @deftypefnx {Function File} {} cylinder (@var{r}, @var{n})
+## @deftypefnx {Function File} {[@var{x}, @var{y}, @var{z}] =} cylinder (@dots{})
+## @deftypefnx {Function File} {} cylinder (@var{ax}, @dots{})
+## Generate three matrices in @code{meshgrid} format, such that
+## @code{surf (@var{x}, @var{y}, @var{z})} generates a unit cylinder.
+## The matrices are of size @code{@var{n}+1}-by-@code{@var{n}+1}.
+## @var{r} is a vector containing the radius along the z-axis.
+## If @var{n} or @var{r} are omitted then default values of 20 or [1 1]
+## are assumed.
+##
+## Called with no return arguments, @code{cylinder} calls directly
+## @code{surf (@var{x}, @var{y}, @var{z})}.  If an axes handle @var{ax}
+## is passed as the first argument, the surface is plotted to this set
+## of axes.
+##
+## Examples:
+##
+## @example
+## @group
+## [x, y, z] = cylinder (10:-1:0, 50);
+## surf (x, y, z);
+## title ("a cone");
+## @end group
+## @end example
+## @seealso{sphere}
+## @end deftypefn
+
+function [xx, yy, zz] = cylinder (varargin)
+
+  [ax, args, nargs] = __plt_get_axis_arg__ ((nargout > 0), "cylinder",
+                                            varargin{:});
+
+  if (nargs == 0)
+    n = 20;
+    r = [1, 1];
+  elseif (nargs == 1)
+    n = 20;
+    r = args{1};
+  elseif (nargs == 2)
+    r = args{1};
+    n = args{2};
+  else
+    print_usage ();
+  endif
+
+  if (length (r) < 2)
+    error ("cylinder: length(R) must be larger than 2");
+  endif
+
+  phi = linspace (0, 2*pi, n+1);
+  idx = 1:length(r);
+  [phi, idx] = meshgrid(phi, idx);
+  z = (idx - 1) / (length(r) - 1);
+  r = r(idx);
+  [x, y] = pol2cart (phi, r);
+
+  if (nargout > 0)
+    xx = x;
+    yy = y;
+    zz = z;
+  else
+    surf (ax, x, y, z);
+  endif
+
+endfunction
+
+%!demo
+%! clf
+%! [x, y, z] = cylinder (10:-1:0,50);
+%! surf (x, y, z);
+%! title ("a cone")