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1 ## Copyright (C) 1995, 1996, 1997, 1998, 2000, 2002, 2004, 2005, 2006, |
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2 ## 2007 Kurt Hornik |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} cor (@var{x}, @var{y}) |
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22 ## Compute correlation. |
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23 ## |
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24 ## The (@var{i}, @var{j})-th entry of @code{cor (@var{x}, @var{y})} is |
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25 ## the correlation between the @var{i}-th variable in @var{x} and the |
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26 ## @var{j}-th variable in @var{y}. |
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27 ## |
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28 ## @iftex |
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29 ## @tex |
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30 ## $$ |
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31 ## {\rm corrcoef}(x,y) = {{\rm cov}(x,y) \over {\rm std}(x) {\rm std}(y)} |
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32 ## $$ |
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33 ## @end tex |
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34 ## @end iftex |
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35 ## @ifnottex |
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36 ## @example |
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37 ## corrcoef(x,y) = cov(x,y)/(std(x)*std(y)) |
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38 ## @end example |
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39 ## @end ifnottex |
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40 ## |
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41 ## For matrices, each row is an observation and each column a variable; |
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42 ## vectors are always observations and may be row or column vectors. |
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43 ## |
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44 ## @code{cor (@var{x})} is equivalent to @code{cor (@var{x}, @var{x})}. |
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45 ## |
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46 ## Note that the @code{corrcoef} function does the same as @code{cor}. |
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47 ## @end deftypefn |
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48 |
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49 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
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50 ## Description: Compute correlations |
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51 |
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52 function retval = cor (x, y) |
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53 |
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54 if (nargin < 1 || nargin > 2) |
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55 print_usage (); |
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56 endif |
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57 |
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58 if (nargin == 2) |
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59 c = cov (x, y); |
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60 s = std (x)' * std (y); |
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61 retval = c ./ s; |
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62 elseif (nargin == 1) |
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63 c = cov (x); |
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64 s = reshape (sqrt (diag (c)), 1, columns (c)); |
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65 retval = c ./ (s' * s); |
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66 endif |
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67 |
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68 endfunction |
