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1 ## Copyright (C) 1996 John W. Eaton |
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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 ## usage: std (a) |
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21 ## |
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22 ## For vector arguments, std returns the standard deviation of the |
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23 ## values. For matrix arguments, std returns a row vector containing |
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24 ## the standard deviation for each column. |
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25 ## |
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26 ## See also: mean, median |
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27 |
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28 ## Author: jwe |
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29 |
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30 function retval = std (a) |
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31 |
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32 if (nargin != 1) |
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33 usage ("std (a)"); |
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34 endif |
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35 |
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36 nr = rows (a); |
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37 nc = columns (a); |
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38 if (nc == 1 && nr == 1) |
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39 retval = 0; |
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40 elseif (nc == 1 || nr == 1) |
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41 n = length (a); |
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42 retval = sqrt (sumsq (a - mean (a)) / (n - 1)); |
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43 elseif (nr > 1 && nc > 0) |
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44 retval = sqrt (sumsq (a - ones (nr, 1) * mean (a)) / (nr - 1)); |
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45 else |
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46 error ("std: invalid matrix argument"); |
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47 endif |
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48 |
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49 endfunction |
