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1 ## Copyright (C) 1995, 1996, 1997 Kurt Hornik |
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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} {} mean (@var{x}, @var{dim}, @var{opt}) |
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21 ## If @var{x} is a vector, compute the mean of the elements of @var{x} |
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22 ## @iftex |
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23 ## @tex |
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24 ## $$ {\rm mean}(x) = \bar{x} = {1\over N} \sum_{i=1}^N x_i $$ |
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25 ## @end tex |
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26 ## @end iftex |
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27 ## @ifinfo |
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28 ## |
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29 ## @example |
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30 ## mean (x) = SUM_i x(i) / N |
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31 ## @end example |
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32 ## @end ifinfo |
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33 ## If @var{x} is a matrix, compute the mean for each column and return them |
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34 ## in a row vector. |
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35 ## |
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36 ## With the optional argument @var{opt}, the kind of mean computed can be |
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37 ## selected. The following options are recognized: |
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38 ## |
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39 ## @table @code |
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40 ## @item "a" |
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41 ## Compute the (ordinary) arithmetic mean. This is the default. |
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42 ## |
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43 ## @item "g" |
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44 ## Compute the geometric mean. |
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45 ## |
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46 ## @item "h" |
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47 ## Compute the harmonic mean. |
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48 ## @end table |
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49 ## |
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50 ## If the optional argument @var{dim} is supplied, work along dimension |
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51 ## @var{dim}. |
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52 ## |
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53 ## Both @var{dim} and @var{opt} are optional. If both are supplied, |
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54 ## either may appear first. |
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55 ## @end deftypefn |
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56 |
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57 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
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58 ## Description: Compute arithmetic, geometric, and harmonic mean |
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59 |
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60 function y = mean (x, opt1, opt2) |
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61 |
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62 need_dim = 0; |
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63 |
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64 if (nargin == 1) |
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65 opt = "a"; |
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66 need_dim = 1; |
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67 elseif (nargin == 2) |
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68 if (ischar (opt1)) |
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69 opt = opt1; |
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70 need_dim = 1; |
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71 else |
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72 dim = opt1; |
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73 opt = "a"; |
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74 endif |
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75 elseif (nargin == 3) |
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76 if (ischar (opt1)) |
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77 opt = opt1; |
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78 dim = opt2; |
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79 elseif (ischar (opt2)) |
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80 opt = opt2; |
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81 dim = opt1; |
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82 else |
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83 error ("mean: expecting opt to be a string"); |
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84 endif |
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85 else |
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86 print_usage (); |
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87 endif |
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88 |
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89 if (need_dim) |
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90 t = find (size (x) != 1); |
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91 if (isempty (t)) |
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92 dim = 1; |
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93 else |
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94 dim = t(1); |
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95 endif |
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96 endif |
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97 |
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98 if (dim > ndims (x)) |
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99 n = 1; |
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100 else |
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101 sz = size (x); |
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102 n = sz (dim); |
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103 endif |
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104 |
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105 if (strcmp (opt, "a")) |
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106 y = sum (x, dim) / n; |
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107 elseif (strcmp (opt, "g")) |
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108 x(x <= 0) = NaN; |
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109 y = exp (sum (log (x), dim) / n); |
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110 elseif (strcmp (opt, "h")) |
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111 x(x == 0) = NaN; |
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112 y = n ./ sum (1 ./ x, dim); |
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113 else |
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114 error ("mean: option `%s' not recognized", opt); |
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115 endif |
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116 |
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117 endfunction |
