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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: toeplitz (c, r) |
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21 ## |
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22 ## Return the Toeplitz matrix constructed given the first column |
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23 ## c, and (optionally) the first row r. |
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24 ## |
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25 ## If the second argument is omitted, the first row is taken to be the |
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26 ## same as the first column. If the first element of c is not the same |
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27 ## as the first element of r, the first element of c is used. |
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28 ## |
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29 ## See also: hankel, vander, hadamard, hilb, invhib |
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30 |
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31 function retval = toeplitz (c, r) |
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32 |
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33 if (nargin == 1) |
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34 r = c; |
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35 elseif (nargin != 2) |
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36 usage ("toeplitz (c, r)"); |
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37 endif |
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38 |
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39 [c_nr, c_nc] = size (c); |
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40 [r_nr, r_nc] = size (r); |
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41 |
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42 if ((c_nr != 1 && c_nc != 1) || (r_nr != 1 && r_nc != 1)) |
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43 error ("toeplitz: expecting vector arguments"); |
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44 endif |
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45 |
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46 if (c_nc != 1) |
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47 c = c.'; |
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48 endif |
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49 |
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50 if (r_nr != 1) |
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51 r = r.'; |
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52 endif |
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53 |
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54 if (r (1) != c (1)) |
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55 warning ("toeplitz: column wins diagonal conflict"); |
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56 endif |
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57 |
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58 ## If we have a single complex argument, we want to return a |
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59 ## Hermitian-symmetric matrix (actually, this will really only be |
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60 ## Hermitian-symmetric if the first element of the vector is real). |
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61 |
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62 if (nargin == 1) |
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63 c = conj (c); |
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64 c(1) = conj (c(1)); |
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65 endif |
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66 |
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67 ## This should probably be done with the colon operator... |
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68 |
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69 nc = length (r); |
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70 nr = length (c); |
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71 |
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72 retval = zeros (nr, nc); |
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73 |
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74 for i = 1:min (nc, nr) |
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75 retval (i:nr, i) = c (1:nr-i+1); |
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76 endfor |
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77 |
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78 for i = 1:min (nr, nc-1) |
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79 retval (i, i+1:nc) = r (2:nc-i+1); |
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80 endfor |
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81 |
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82 endfunction |
