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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 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, 59 Temple Place - Suite 330, Boston, MA |
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18 ## 02111-1307, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} var (@var{x}) |
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22 ## For vector arguments, return the (real) variance of the values. |
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23 ## For matrix arguments, return a row vector contaning the variance for |
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24 ## each column. |
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25 ## |
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26 ## The argument @var{opt} determines the type of normalization to use. Valid |
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27 ## values are |
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28 ## |
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29 ## @table @asis |
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30 ## @item 0: |
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31 ## normalizes with N-1, provides the square root of best unbiased estimator |
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32 ## of the variance [default] |
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33 ## @item 1: |
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34 ## normalizes with N, this provides the square root of the second moment |
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35 ## around the mean |
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36 ## @end table |
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37 ## |
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38 ## The third argument @var{dim} determines the dimension along which the |
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39 ## variance is calculated. |
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40 ## @end deftypefn |
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41 |
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42 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> |
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43 ## Description: Compute variance |
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44 |
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45 function y = var (x, opt, dim) |
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46 |
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47 if (nargin < 1 || nargin > 3) |
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48 usage ("var (x, opt, sim)"); |
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49 endif |
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50 if (nargin < 3) |
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51 dim = min (find (size (x) > 1)); |
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52 if (isempty (dim)) |
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53 dim = 1; |
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54 endif |
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55 endif |
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56 if (nargin < 2 || isempty (opt)) |
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57 opt = 0; |
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58 endif |
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59 |
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60 sz = size (x); |
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61 if (prod (sz) < 1) |
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62 error ("var: x must not be empty"); |
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63 elseif (sz(dim) == 1) |
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64 y = 0; |
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65 else |
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66 rng = ones (1, length (sz)); |
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67 rng (dim) = sz (dim); |
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68 if (opt == 0) |
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69 y = sumsq (x - repmat(mean (x, dim), rng), dim) / (sz(dim) - 1); |
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70 else |
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71 y = sumsq (x - repmat(mean (x, dim), rng), dim) / sz(dim); |
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72 endif |
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73 endif |
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74 |
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75 endfunction |
