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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} {} studentize (@var{x}) |
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19 ## If @var{x} is a vector, subtract its mean and divide by its standard |
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20 ## deviation. |
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21 ## |
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22 ## If @var{x} is a matrix, do the above for each column. |
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23 ## @end deftypefn |
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24 |
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25 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> |
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26 ## Description: Subtract mean and divide by standard deviation |
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27 |
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28 function t = studentize (x) |
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29 |
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30 if (nargin != 1) |
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31 usage ("studentize (x)"); |
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32 endif |
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33 |
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34 if is_vector (x) |
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35 if (std (x) == 0) |
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36 t = zeros (size (x)); |
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37 else |
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38 t = (x - mean (x)) / std (x); |
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39 endif |
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40 elseif is_matrix (x) |
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41 l = ones (rows (x), 1); |
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42 t = x - l * mean (x); |
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43 t = t ./ (l * max ([(std (t)); (! any (t))])); |
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44 else |
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45 error ("studentize: x must be a vector or a matrix."); |
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46 endif |
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47 |
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48 endfunction |
