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1 ## Copyright (C) 2003, 2007 Shai Ayal |
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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} {[@var{c}, @var{lev}] =} contourc (@var{x}, @var{y}, @var{z}, @var{vn}) |
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21 ## Compute isolines (countour lines) of the matrix @var{z}. |
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22 ## Parameters @var{x}, @var{y} and @var{vn} are optional. |
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23 ## |
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24 ## The return value @var{lev} is a vector of the contour levels. |
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25 ## The return value @var{c} is a 2 by @var{n} matrix containing the |
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26 ## contour lines in the following format |
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27 ## |
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28 ## @example |
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29 ## @var{c} = [lev1, x1, x2, ..., levn, x1, x2, ... |
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30 ## len1, y1, y2, ..., lenn, y1, y2, ...] |
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31 ## @end example |
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32 ## |
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33 ## @noindent |
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34 ## in which contour line @var{n} has a level (height) of @var{levn} and |
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35 ## length of @var{lenn}. |
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36 ## |
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37 ## If @var{x} and @var{y} are omitted they are taken as the row/column |
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38 ## index of @var{z}. @var{vn} is either a scalar denoting the number of lines |
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39 ## to compute or a vector containing the values of the lines. If only one |
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40 ## value is wanted, set @code{@var{vn} = [val, val]}; |
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41 ## If @var{vn} is omitted it defaults to 10. |
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42 ## |
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43 ## For example, |
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44 ## @example |
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45 ## @group |
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46 ## x = 0:2; |
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47 ## y = x; |
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48 ## z = x' * y; |
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49 ## contourc (x, y, z, 2:3) |
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50 ## @result{} 2.0000 2.0000 1.0000 3.0000 1.5000 2.0000 |
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51 ## 2.0000 1.0000 2.0000 2.0000 2.0000 1.5000 |
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52 ## |
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53 ## @end group |
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54 ## @end example |
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55 ## @seealso{contour} |
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56 ## @end deftypefn |
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57 |
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58 ## Author: Shai Ayal <shaiay@users.sourceforge.net> |
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59 |
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60 function [cout, lev] = contourc (varargin) |
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61 |
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62 if (nargin == 1) |
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63 vn = 10; |
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64 z = varargin{1}; |
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65 [nr, nc] = size (z); |
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66 x = 1:nc; |
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67 y = 1:nr; |
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68 elseif (nargin == 2) |
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69 vn = varargin{2}; |
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70 z = varargin{1}; |
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71 [nr, nc] = size (z); |
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72 x = 1:nc; |
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73 y = 1:nr; |
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74 elseif (nargin == 3) |
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75 vn = 10; |
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76 x = varargin{1}; |
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77 y = varargin{2}; |
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78 z = varargin{3}; |
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79 elseif (nargin == 4) |
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80 vn = varargin{4}; |
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81 x = varargin{1}; |
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82 y = varargin{2}; |
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83 z = varargin{3}; |
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84 else |
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85 print_usage (); |
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86 endif |
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87 |
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88 if (isscalar (vn)) |
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89 vv = linspace (min (z(:)), max (z(:)), vn+2)(2:end-1); |
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90 else |
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91 vv = unique (sort (vn)); |
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92 endif |
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93 |
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94 if (isvector (x) && isvector (y)) |
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95 c = __contourc__ (x(:)', y(:)', z, vv); |
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96 else |
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97 ## Indexes x,y for the purpose of __contourc__. |
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98 ii = 1:size (z,2); |
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99 jj = 1:size (z,1); |
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100 |
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101 ## Now call __contourc__ for the real work... |
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102 c = __contourc__ (ii, jj, z, vv); |
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103 |
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104 ## Map the contour lines from index space (i,j) back |
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105 ## to the original grid (x,y) |
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106 i = 1; |
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107 |
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108 while (i < size (c,2)) |
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109 clen = c(2, i); |
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110 ind = i + [1 : clen]; |
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111 |
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112 ci = c(1, ind); |
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113 cj = c(2,ind); |
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114 |
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115 ## due to rounding errors some elements of ci and cj |
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116 ## can fall out of the range of ii and jj and interp2 would |
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117 ## return NA for those values. |
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118 ## The permitted range is enforced here: |
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119 |
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120 ci = max (ci, 1); ci = min (ci, size (z, 2)); |
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121 cj = max (cj, 1); cj = min (cj, size (z, 1)); |
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122 |
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123 c(1, ind) = interp2 (ii, jj, x, ci, cj); |
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124 c(2, ind) = interp2 (ii, jj, y, ci, cj); |
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125 |
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126 i = i + clen + 1; |
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127 endwhile |
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128 endif |
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129 |
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130 if (nargout > 0) |
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131 cout = c; |
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132 lev = vv; |
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133 endif |
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134 |
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135 endfunction |
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136 |
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137 %!demo |
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138 %! x = 0:2; |
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139 %! y = x; |
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140 %! z = x' * y; |
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141 %! contourc (x, y, z, 2:3) |
