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1 ## Copyright (C) 2000 Kai Habel |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} voronoi (@var{x}, @var{y}) |
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21 ## @deftypefnx {Function File} {} voronoi (@var{x}, @var{y}, "plotstyle") |
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22 ## @deftypefnx {Function File} {} voronoi (@var{x}, @var{y}, "plotstyle", @var{options}) |
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23 ## @deftypefnx {Function File} {[@var{vx}, @var{vy}] =} voronoi (@dots{}) |
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24 ## plots voronoi diagram of points @code{(@var{x}, @var{y})}. |
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25 ## The voronoi facets with points at infinity are not drawn. |
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26 ## [@var{vx}, @var{vy}] = voronoi(...) returns the vertices instead plotting the |
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27 ## diagram. plot (@var{vx}, @var{vy}) shows the voronoi diagram. |
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28 ## |
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29 ## A fourth optional argument, which must be a string, contains extra options |
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30 ## passed to the underlying qhull command. See the documentation for the |
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31 ## Qhull library for details. |
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32 ## |
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33 ## @example |
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34 ## @group |
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35 ## x = rand (10, 1); |
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36 ## y = rand (size (x)); |
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37 ## h = convhull (x, y); |
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38 ## [vx, vy] = voronoi (x, y); |
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39 ## plot (vx, vy, "-b", x, y, "o", x(h), y(h), "-g") |
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40 ## legend ("", "points", "hull"); |
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41 ## @end group |
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42 ## @end example |
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43 ## |
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44 ## @seealso{voronoin, delaunay, convhull} |
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45 ## @end deftypefn |
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46 |
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47 ## Author: Kai Habel <kai.habel@gmx.de> |
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48 ## First Release: 20/08/2000 |
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49 |
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50 ## 2002-01-04 Paul Kienzle <pkienzle@users.sf.net> |
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51 ## * limit the default graph to the input points rather than the whole diagram |
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52 ## * provide example |
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53 ## * use unique(x,"rows") rather than __unique_rows__ |
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54 |
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55 ## 2003-12-14 Rafael Laboissiere <rafael@laboissiere.net> |
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56 ## Added optional fourth argument to pass options to the underlying |
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57 ## qhull command |
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58 |
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59 function [vvx, vvy] = voronoi (varargin) |
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60 |
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61 if (nargin < 1) |
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62 print_usage (); |
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63 endif |
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64 |
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65 narg = 1; |
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66 if (isscalar (varargin{1}) && ishandle (varargin{1})) |
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67 handl = varargin{1}; |
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68 narg++; |
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69 if (! strcmp (get (handl, "type"), "axes")) |
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70 error ("voronoi: expecting first argument to be an axes object"); |
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71 endif |
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72 else |
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73 if (nargout < 2) |
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74 handl = gca (); |
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75 endif |
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76 endif |
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77 |
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78 if (nargin < 1 + narg || nargin > 3 + narg) |
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79 print_usage (); |
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80 endif |
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81 |
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82 x = varargin{narg++}; |
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83 y = varargin{narg++}; |
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84 |
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85 opts = {}; |
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86 if (narg <= nargin) |
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87 if (iscell (varargin{narg})) |
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88 opts = varargin(narg++); |
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89 elseif (ismatrix (varargin{narg})) |
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90 ## Accept but ignore the triangulation |
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91 narg++; |
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92 endif |
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93 endif |
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94 |
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95 linespec = {"b"}; |
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96 if (narg <= nargin) |
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97 if (ischar (varargin{narg})) |
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98 linespec = varargin(narg); |
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99 endif |
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100 endif |
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101 |
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102 lx = length (x); |
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103 ly = length (y); |
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104 |
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105 if (lx != ly) |
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106 error ("voronoi: arguments must be vectors of same length"); |
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107 endif |
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108 |
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109 ## Add big box to approximate rays to infinity |
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110 xmax = max (x(:)); |
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111 xmin = min (x(:)); |
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112 ymax = max (y(:)); |
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113 ymin = min (y(:)); |
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114 xdelta = xmax - xmin; |
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115 ydelta = ymax - ymin; |
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116 scale = 10e4; |
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117 |
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118 xbox = [xmin - scale * xdelta; xmin - scale * xdelta; ... |
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119 xmax + scale * xdelta; xmax + scale * xdelta]; |
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120 ybox = [xmin - scale * xdelta; xmax + scale * xdelta; ... |
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121 xmax + scale * xdelta; xmin - scale * xdelta]; |
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122 x = [x(:) ; xbox(:)]; |
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123 y = [y(:) ; ybox(:)]; |
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124 |
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125 [p, c, infi] = __voronoi__ ([x(:), y(:)], opts{:}); |
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126 |
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127 idx = find (!infi); |
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128 |
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129 ll = length (idx); |
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130 k = 0;r = 1; |
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131 |
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132 for i = 1 : ll |
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133 k += length (c{idx(i)}); |
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134 endfor |
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135 |
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136 edges = zeros (2, k); |
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137 |
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138 for i = 1 : ll |
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139 fac = c {idx(i)}; |
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140 lf = length (fac); |
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141 fac = [fac, fac(1)]; |
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142 fst = fac (1 : length(fac) - 1); |
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143 sec = fac(2 : length(fac)); |
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144 edges (:, r : r + lf - 1) = [fst; sec]; |
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145 r += lf; |
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146 endfor |
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147 |
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148 ## Identify the unique edges of the Voronoi diagram |
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149 edges = sortrows (sort (edges).').'; |
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150 edges = edges (:, [(edges(1, 1: end - 1) != edges(1, 2 : end) | ... |
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151 edges(2, 1 :end - 1) != edges(2, 2 : end)), true]); |
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152 |
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153 ## Eliminate the edges of the diagram representing the box |
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154 poutside = (1 : rows(p)) ... |
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155 (p (:, 1) < xmin - xdelta | p (:, 1) > xmax + xdelta | ... |
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156 p (:, 2) < ymin - ydelta | p (:, 2) > ymax + ydelta); |
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157 edgeoutside = ismember (edges (1, :), poutside) & ... |
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158 ismember (edges (2, :), poutside); |
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159 edges (:, edgeoutside) = []; |
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160 |
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161 ## Get points of the diagram |
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162 vx = reshape (p (edges, 1), size(edges)); |
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163 vy = reshape (p (edges, 2), size(edges)); |
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164 |
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165 if (nargout < 2) |
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166 lim = [xmin, xmax, ymin, ymax]; |
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167 h = plot (handl, vx, vy, linespec{:}, x, y, '+'); |
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168 axis (lim + 0.1 * [[-1, 1] * (lim (2) - lim (1)), ... |
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169 [-1, 1] * (lim (4) - lim (3))]); |
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170 if (nargout == 1) |
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171 vxx = h; |
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172 endif |
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173 elseif (nargout == 2) |
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174 vvx = vx; |
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175 vvy = vy; |
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176 else |
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177 error ("voronoi: only two or zero output arguments supported") |
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178 endif |
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179 |
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180 endfunction |
