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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 ## prepad (x, l) |
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21 ## |
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22 ## Prepends zeros to the vector x until it is of length l. |
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23 ## prepad(x,l,c) prepends the constant c instead of zero. |
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24 ## |
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25 ## If length (x) > l, elements from the beginning of x are removed |
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26 ## until a vector of length l is obtained. |
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27 |
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28 function y = prepad (x, l, c) |
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29 |
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30 ## Author: |
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31 ## Tony Richardson |
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32 ## amr@mpl.ucsd.edu |
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33 ## June 1994 |
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34 |
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35 if (nargin == 2) |
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36 c = 0; |
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37 elseif (nargin < 2 || nargin > 3) |
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38 usage ("prepad (x, l) or prepad (x, l, c)"); |
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39 endif |
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40 |
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41 if (is_matrix (x)) |
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42 error ("first argument must be a vector"); |
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43 elseif (! is_scalar (l)) |
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44 error ("second argument must be a scaler"); |
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45 endif |
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46 |
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47 if (l < 0) |
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48 error ("second argument must be non-negative"); |
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49 endif |
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50 |
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51 lx = length (x); |
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52 |
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53 if (lx >= l) |
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54 y = x(lx-l+1:lx); |
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55 else |
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56 if (rows (x) > 1) |
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57 tmp = c * ones (l-lx, 1); |
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58 y = [tmp; x]; |
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559
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59 else |
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60 tmp = c * ones (1, l-lx); |
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61 y = [tmp, x]; |
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62 endif |
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63 endif |
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64 |
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65 endfunction |
