Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / miscellaneous-1.1.0 / hilbert_curve.m

diff --git a/octave_packages/miscellaneous-1.1.0/hilbert_curve.m b/octave_packages/miscellaneous-1.1.0/hilbert_curve.m
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+## Copyright (C) 2009 Javier Enciso <j4r.e4o@gmail.com>
+##
+## This program 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.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function file} {@var{x}, @var{y}} hilbert_curve (@var{n})
+## Creates an iteration of the Hilbert space-filling curve with @var{n} points. 
+## The argument @var{n} must be of the form @code{2^M}, where @var{m} is an 
+## integer greater than 0.
+## 
+## @example
+## n = 8
+## [x ,y] = hilbert_curve (n);
+## line (x, y, "linewidth", 4, "color", "blue");
+## @end example
+## 
+## @end deftypefn
+
+function [x, y] = hilbert_curve (n)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+  
+  check_power_of_two (n);
+  if (n == 2)
+    x = [0, 0, 1, 1];
+    y = [0, 1, 1, 0];
+  else
+    [x1, y1] = hilbert_curve (n/2);
+    x = [y1, x1, n/2 + x1, n - 1 - y1];
+    y = [x1, n/2 + y1, n/2 + y1, n/2 - 1 - x1];
+  endif
+  
+endfunction
+
+function check_power_of_two (n)
+  if (frac_part (log (n) / log (2)) != 0)
+    error ("hilbert_curve: input argument must be a power of 2.")
+  endif
+endfunction
+
+function d = frac_part (f)
+  d = f - floor (f);
+endfunction
+
+%!test
+%! n = 2;
+%! expect = [0, 0, 1, 1; 0, 1, 1, 0];
+%! [get(1,:), get(2,:)] = hilbert_curve (n);
+%! if (any(size (expect) != size (get)))
+%!   error ("wrong size: expected %d,%d but got %d,%d", size (expect), size (get));
+%! elseif (any (any (expect!=get)))
+%!   error ("didn't get what was expected.");
+%! endif
+
+%!test
+%! n = 5;
+%!error hilbert_curve (n);
+
+%!demo
+%! clf
+%! n = 4;
+%! [x, y] = hilbert_curve (n);
+%! line (x, y, "linewidth", 4, "color", "blue");
+%! % -----------------------------------------------------------------------
+%! % the figure window shows an iteration of the Hilbert space-fillig curve 
+%! % with 4 points on each axis.
+
+%!demo
+%! clf
+%! n = 64;
+%! [x, y] = hilbert_curve (n);
+%! line (x, y, "linewidth", 2, "color", "blue");
+%! % ----------------------------------------------------------------------
+%! % the figure window shows an iteration of the Hilbert space-fillig curve 
+%! % with 64 points on each axis.