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1 ## Copyright (C) 1995, 1996, 1997 Kurt Hornik |
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2 ## |
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3 ## This program is free software; you can redistribute it and/or modify |
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4 ## it under the terms of the GNU General Public License as published by |
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5 ## the Free Software Foundation; either version 2, or (at your option) |
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6 ## any later version. |
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7 ## |
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8 ## This program is distributed in the hope that it will be useful, but |
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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11 ## General Public License for more details. |
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12 ## |
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13 ## You should have received a copy of the GNU General Public License |
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14 ## along with this file. If not, write to the Free Software Foundation, |
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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16 |
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17 ## -*- texinfo -*- |
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18 ## @deftypefn {Function File} {} mean (@var{x}, @var{opt}) |
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19 ## If @var{x} is a vector, compute the mean of the elements of @var{x} |
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20 ## @iftex |
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21 ## @tex |
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22 ## $$ {\rm mean}(x) = \bar{x} = {1\over N} \sum_{i=1}^N x_i $$ |
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23 ## @end tex |
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24 ## @end iftex |
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25 ## @ifinfo |
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26 ## |
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27 ## @example |
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28 ## mean (x) = SUM_i x(i) / N |
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29 ## @end example |
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30 ## @end ifinfo |
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31 ## If @var{x} is a matrix, compute the mean for each column and return them |
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32 ## in a row vector. |
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33 ## |
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34 ## With the optional argument @var{opt}, the kind of mean computed can be |
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35 ## selected. The following options are recognized: |
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36 ## |
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37 ## @table @code |
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38 ## @item "a" |
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39 ## Compute the (ordinary) arithmetic mean. This is the default. |
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40 ## |
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41 ## @item "g" |
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42 ## Computer the geometric mean. |
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43 ## |
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44 ## @item "h" |
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45 ## Compute the harmonic mean. |
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46 ## @end table |
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47 ## @end deftypefn |
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48 |
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49 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> |
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50 ## Description: Compute arithmetic, geometric, and harmonic mean |
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51 |
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52 function y = mean (x, opt) |
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53 |
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54 if ((nargin < 1) || (nargin > 2)) |
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55 usage ("mean (x [, opt])"); |
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56 endif |
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57 |
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58 if isempty (x) |
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59 error ("mean: x must not be empty"); |
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60 endif |
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61 |
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62 if (rows (x) == 1) |
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63 x = x.'; |
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64 endif |
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65 |
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66 if (nargin == 1) |
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67 opt = "a"; |
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68 endif |
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69 |
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70 [r, c] = size (x); |
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71 |
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72 if (strcmp (opt, "a")) |
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73 y = sum (x) / r; |
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74 elseif (strcmp (opt, "g")) |
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75 y = NaN * ones (1, c); |
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76 i = find (all (x > 0)); |
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77 if any (i) |
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78 y(i) = exp (sum (log (x(:, i))) / r); |
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79 endif |
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80 elseif (strcmp (opt, "h")) |
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81 y = NaN * ones (1, c); |
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82 i = find (all (x != 0)); |
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83 if any (i) |
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84 y(i) = r ./ sum (1 ./ x(:, i)); |
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85 endif |
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86 else |
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87 error (sprintf ("mean: option `%s' not recognized", opt)); |
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88 endif |
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89 |
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90 endfunction |
