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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} {} autoreg_matrix (@var{y}, @var{k}) |
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22 ## Given a time series (vector) @var{y}, return a matrix with ones in the |
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23 ## first column and the first @var{k} lagged values of @var{y} in the |
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24 ## other columns. I.e., for @var{t} > @var{k}, @code{[1, |
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25 ## @var{y}(@var{t}-1), ..., @var{y}(@var{t}-@var{k})]} is the t-th row |
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26 ## of the result. The resulting matrix may be used as a regressor matrix |
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27 ## in autoregressions. |
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28 ## @end deftypefn |
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29 |
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30 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> |
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31 ## Description: Design matrix for autoregressions |
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32 |
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33 function X = autoreg_matrix (y, k) |
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34 |
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35 if (nargin != 2) |
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36 usage ("autoreg_matrix (y, k)"); |
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37 endif |
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38 |
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39 if (! (isvector (y))) |
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40 error ("autoreg_matrix: y must be a vector"); |
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41 endif |
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42 |
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43 T = length (y); |
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44 y = reshape (y, T, 1); |
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45 X = ones (T, k+1); |
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46 for j = 1 : k; |
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47 X(:, j+1) = [(zeros (j, 1)); y(1:T-j)]; |
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48 endfor |
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49 |
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50 endfunction |