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[project @ 2007-10-12 21:27:11 by jwe]
author jwe
date Fri, 12 Oct 2007 21:27:37 +0000
parents 93c65f2a5668
children 83a8781b529d 377d908f7e40
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 ## Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2002, 2004,
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2 ## 2005, 2006, 2007 John W. Eaton
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3 ##
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4 ## This file is part of Octave.
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5 ##
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6 ## Octave is free software; you can redistribute it and/or modify it
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7 ## under the terms of the GNU General Public License as published by
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8 ## the Free Software Foundation; either version 3 of the License, or (at
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9 ## your option) any later version.
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10 ##
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11 ## Octave is distributed in the hope that it will be useful, but
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 ## General Public License for more details.
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15 ##
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16 ## You should have received a copy of the GNU General Public License
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17 ## along with Octave; see the file COPYING. If not, see
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18 ## <http://www.gnu.org/licenses/>.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {} polyval (@var{c}, @var{x})
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22 ## Evaluate a polynomial.
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23 ##
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24 ## @code{polyval (@var{c}, @var{x})} will evaluate the polynomial at the
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25 ## specified value of @var{x}.
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26 ##
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27 ## If @var{x} is a vector or matrix, the polynomial is evaluated at each of
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28 ## the elements of @var{x}.
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29 ## @seealso{polyvalm, poly, roots, conv, deconv, residue, filter,
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30 ## polyderiv, polyinteg}
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31 ## @end deftypefn
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32
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33 ## Author: Tony Richardson <arichard@stark.cc.oh.us>
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34 ## Created: June 1994
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35 ## Adapted-By: jwe
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36
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37 function y = polyval (c, x)
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38
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39 if (nargin != 2)
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40 print_usage ();
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41 endif
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42
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43 if (! (isvector (c) || isempty (c)))
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44 error ("polyval: first argument must be a vector");
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45 endif
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46
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47 if (isempty (x))
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48 y = [];
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49 return;
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50 endif
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51
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52 if (length (c) == 0)
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53 y = c;
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54 return;
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55 endif
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56
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57 n = length (c);
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58 y = c (1) * ones (rows (x), columns (x));
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59 for index = 2:n
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60 y = c (index) + x .* y;
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61 endfor
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62
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63 endfunction