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1 ## Copyright (C) 1996 Auburn University. All rights reserved. |
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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 the |
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7 ## Free Software Foundation; either version 2, or (at your option) any |
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8 ## later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 ## 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 02111 USA. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} zgshsr (@var{y}) |
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21 ## apply householder vector based on @math{e^(m)} to |
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22 ## (column vector) y. |
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23 ## Called by zgfslv |
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24 ## @end deftypefn |
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25 |
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26 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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27 ## Created: July 24, 1992 |
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28 ## Conversion to Octave by R. Bruce Tenison July 3, 1994 |
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29 |
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30 function x = zgshsr (y) |
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31 |
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32 if (! isvector (y)) |
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33 error (sprintf ("y(%dx%d) must be a vector", rows (y), columns (y))); |
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34 endif |
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35 x = vec (y); |
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36 m = length (x); |
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37 if (m > 1) |
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38 beta = (1 + sqrt (m)) * x(1) + sum (x(2:m)); |
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39 beta /= (m + sqrt (m)); |
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40 x(1) -= (beta * (1 + sqrt (m))); |
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41 x(2:m) -= (beta * ones (m-1,1)); |
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42 else |
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43 x = -x; |
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44 endif |
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45 |
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46 endfunction |
