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1 ## Copyright (C) 1996, 1997 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 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} prepad (@var{x}, @var{l}, @var{c}) |
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22 ## @deftypefnx {Function File} {} postpad (@var{x}, @var{l}, @var{c}) |
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23 ## @deftypefnx {Function File} {} postpad (@var{x}, @var{l}, @var{c}, @var{dim}) |
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24 ## |
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25 ## Prepends (appends) the scalar value @var{c} to the vector @var{x} |
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26 ## until it is of length @var{l}. If the third argument is not |
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27 ## supplied, a value of 0 is used. |
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28 ## |
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29 ## If @code{length (@var{x}) > @var{l}}, elements from the beginning (end) of |
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30 ## @var{x} are removed until a vector of length @var{l} is obtained. |
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31 ## |
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32 ## If @var{x} is a matrix, elements are prepended or removed from each row. |
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33 ## |
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34 ## If the optional @var{dim} argument is given, then operate along this |
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35 ## dimension. |
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36 ## @end deftypefn |
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37 |
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38 ## Author: Tony Richardson <arichard@stark.cc.oh.us> |
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39 ## Created: June 1994 |
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40 |
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41 function y = prepad (x, l, c, dim) |
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42 |
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43 if (nargin < 2 || nargin > 4) |
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44 usage ("prepad (x, l, [c, [dim]])"); |
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45 endif |
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46 |
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47 if (nargin < 3 || isempty (c)) |
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48 c = 0; |
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49 else |
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50 if (! isscalar (c)) |
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51 error ("prepad: third argument must be empty or a scalar"); |
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52 endif |
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53 endif |
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54 |
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55 nd = ndims (x); |
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56 sz = size (x); |
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57 if (nargin < 4) |
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58 %% Find the first non-singleton dimension |
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59 dim = 1; |
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60 while (dim < nd + 1 && sz (dim) == 1) |
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61 dim = dim + 1; |
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62 endwhile |
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63 if (dim > nd) |
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64 dim = 1; |
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65 endif |
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66 else |
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67 if (! (isscalar (dim) && dim == round (dim)) && dim > 0 && |
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68 dim < (nd + 1)) |
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69 error ("prepad: dim must be an integer and valid dimension"); |
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70 endif |
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71 endif |
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72 |
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73 if (! ismatrix (x)) |
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74 error ("first argument must be a vector or matrix"); |
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75 elseif (! isscalar (l) || l < 0) |
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76 error ("second argument must be a positive scaler"); |
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77 endif |
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78 |
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79 d = sz (dim); |
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80 |
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81 if (d >= l) |
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82 idx = cell (); |
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83 for i = 1:nd |
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84 idx {i} = 1:sz(i); |
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85 endfor |
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86 idx {dim} = d-l+1:d; |
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87 y = x (idx {:}); |
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88 else |
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89 sz (dim) = l - d; |
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90 y = cat (dim, c * ones (sz), x); |
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91 endif |
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92 |
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93 endfunction |
