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1 ## Copyright (C) 2007 David Bateman |
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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 2, or (at your option) |
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8 ## 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, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {[@var{m}, @var{f}, @var{c}] =} mode (@var{x}, @var{dim}) |
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22 ## Count the most frequently appearing value. @code{mode} counts the |
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23 ## frequency along the first non-singleton dimension and if two or more |
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24 ## values have te same frequency returns the smallest of the two in |
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25 ## @var{m}. The dimension along which to count can be specified by the |
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26 ## @var{dim} parameter. |
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27 ## |
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28 ## The variable @var{f} counts the frequency of each of the most frequently |
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29 ## occurring elements. The cell array @var{c} contains all of the elements |
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30 ## with the maximum frequency . |
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31 ## @end deftypefn |
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32 |
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33 function [m, f, c] = mode (x, dim) |
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34 |
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35 if (nargin < 1 || nargin > 2) |
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36 print_usage (); |
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37 endif |
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38 |
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39 nd = ndims (x); |
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40 sz = size (x); |
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41 |
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42 if (nargin != 2) |
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43 ## Find the first non-singleton dimension. |
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44 dim = 1; |
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45 while (dim < nd + 1 && sz(dim) == 1) |
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46 dim = dim + 1; |
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47 endwhile |
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48 if (dim > nd) |
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49 dim = 1; |
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50 endif |
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51 else |
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52 if (! (isscalar (dim) && dim == round (dim)) |
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53 && dim > 0 |
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54 && dim < (nd + 1)) |
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55 error ("mode: dim must be an integer and valid dimension"); |
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56 endif |
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57 endif |
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58 |
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59 sz2 = sz; |
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60 sz2 (dim) = 1; |
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61 sz3 = ones (1, nd); |
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62 sz3 (dim) = sz (dim); |
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63 |
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64 if (dim != 1) |
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65 perm = [1 : nd]; |
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66 perm(1) = dim; |
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67 perm(dim) = 1; |
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68 endif |
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69 |
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70 xs = sort (x, dim); |
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71 t = cat (dim, true (sz2), diff (xs, 1, dim) != 0); |
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72 if (issparse (x)) |
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73 t2 = sparse (sz(1), sz(2)); |
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74 else |
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75 t2 = zeros (size (t)); |
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76 endif |
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77 |
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78 if (dim != 1) |
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79 t2 (permute (t != 0, perm)) = diff ([find(permute (t, perm)); prod(sz)+1]); |
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80 f = max (ipermute (t2, perm), [], dim); |
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81 xs = permute (xs, perm); |
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82 else |
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83 t2 (t) = diff ([find(t); prod(sz)+1]); |
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84 f = max (t2, [], dim); |
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85 endif |
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86 |
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87 c = cell (sz2); |
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88 m = zeros (sz2); |
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89 for i = 1 : prod (sz2) |
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90 c {i} = xs (t2 (:, i) == f(i), i); |
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91 m (i) = c{i}(1); |
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92 endfor |
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93 endfunction |
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94 |
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95 %!test |
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96 %! [m, f, c] = mode (toeplitz (1:5)); |
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97 %! assert (m, [1,2,2,2,1]); |
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98 %! assert (f, [1,2,2,2,1]); |
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99 %! assert (c, {[1;2;3;4;5],[2],[2;3],[2],[1;2;3;4;5]}); |
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100 %!test |
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101 %! [m, f, c] = mode (toeplitz (1:5), 2); |
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102 %! assert (m, [1;2;2;2;1]); |
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103 %! assert (f, [1;2;2;2;1]); |
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104 %! assert (c, {[1;2;3;4;5];[2];[2;3];[2];[1;2;3;4;5]}); |
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105 %!test |
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106 %! a = sprandn (32, 32, 0.05); |
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107 %! [m, f, c] = mode (a); |
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108 %! [m2, f2, c2] = mode (full (a)); |
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109 %! assert (m, m2); |
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110 %! assert (f, f2); |
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111 %! assert (c, c2); |
