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−## Copyright (C) 2008-2012 Ben Abbott
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−##
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−## This file is part of Octave.
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−##
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−## Octave is free software; you can redistribute it and/or modify it
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−## under the terms of the GNU General Public License as published by
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−## the Free Software Foundation; either version 3 of the License, or (at
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−## your option) any later version.
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−##
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−## Octave is distributed in the hope that it will be useful, but
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−## WITHOUT ANY WARRANTY; without even the implied warranty of
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−## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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−## General Public License for more details.
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−##
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−## You should have received a copy of the GNU General Public License
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−## along with Octave; see the file COPYING.  If not, see
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−## <http://www.gnu.org/licenses/>.
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−
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−## -*- texinfo -*-
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−## @deftypefn  {Function File} {} comet (@var{y})
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−## @deftypefnx {Function File} {} comet (@var{x}, @var{y})
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−## @deftypefnx {Function File} {} comet (@var{x}, @var{y}, @var{p})
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−## @deftypefnx {Function File} {} comet (@var{ax}, @dots{})
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−## Produce a simple comet style animation along the trajectory provided by
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−## the input coordinate vectors (@var{x}, @var{y}), where @var{x} will default
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−## to the indices of @var{y}.
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−##
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−## The speed of the comet may be controlled by @var{p}, which represents the
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−## time which passes as the animation passes from one point to the next.  The
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−## default for @var{p} is 0.1 seconds.
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−##
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−## If @var{ax} is specified the animation is produced in that axis rather than
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−## the @code{gca}.
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−## @end deftypefn
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−
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−## Author: Ben Abbott bpabbott@mac.com
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−## Created: 2008-09-21
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−
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−function comet (varargin)
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−
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−  [h, varargin, nargin] = __plt_get_axis_arg__ ("comet", varargin{:});
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−
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−  if (nargin == 0)
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−    print_usage ();
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−  elseif (nargin == 1)
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−    y = varargin{1};
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−    x = 1:numel (y);
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−    p = 0.1;
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−  elseif (nargin == 2)
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−    x = varargin{1};
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−    y = varargin{2};
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−    p = 0.1;
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−  elseif (nargin == 3)
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−    x = varargin{1};
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−    y = varargin{2};
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−    p = varargin{3};
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−  endif
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−
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−  oldh = gca ();
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−  unwind_protect
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−    axes (h);
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−    newplot ();
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−    theaxis = [min(x), max(x), min(y), max(y)];
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−    num = numel (y);
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−    dn = round (num/10);
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−    for n = 1:(num+dn);
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−      m = n - dn;
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−      m = max ([m, 1]);
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−      k = min ([n, num]);
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−      h = plot (x(1:m), y(1:m), "r", x(m:k), y(m:k), "g", x(k), y(k), "ob");
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−      axis (theaxis);
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−      drawnow ();
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−      pause (p);
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−    endfor
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−  unwind_protect_cleanup
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−    axes (oldh);
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−  end_unwind_protect
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−
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−endfunction
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−
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−
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−%!demo
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−%! clf;
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−%! t = 0:.1:2*pi;
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−%! x = cos (2*t) .* (cos (t).^2);
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−%! y = sin (2*t) .* (sin (t).^2);
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−%! comet (x, y);
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−