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annotate scripts/polynomial/ppval.m @ 6046:34f96dd5441b

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[project @ 2006-10-10 16:10:25 by jwe]
author jwe
date Tue, 10 Oct 2006 16:10:31 +0000
parents 437f9086b967
children 93c65f2a5668
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1 ## Copyright (C) 2000 Paul Kienzle
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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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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18 ## 02110-1301, USA.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {@var{yi} =} ppval (@var{pp}, @var{xi})
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22 ## Evaluate piece-wise polynomial @var{pp} at the points @var{xi}.
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23 ## If @code{@var{pp}.d} is a scalar greater than 1, or an array,
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24 ## then the returned value @var{yi} will be an array that is
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25 ## @code{d1, d1, @dots{}, dk, length (@var{xi})]}.
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26 ## @seealso{mkpp, unmkpp, spline}
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27 ## @end deftypefn
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28
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29 function yi = ppval (pp, xi)
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30
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31 if (nargin != 2)
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32 print_usage ();
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33 endif
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34 if (! isstruct (pp))
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35 error ("ppval: expects a pp structure");
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36 endif
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37 if (isempty (xi))
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38 yi = [];
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39 else
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40 transposed = (columns (xi) == 1);
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41 xi = xi(:);
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42 xn = length (xi);
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43 idx = lookup (pp.x(2:pp.n), xi) + 1;
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44 dx = (xi - pp.x(idx)).';
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45 dx = reshape (dx(ones(1,prod(pp.d)),:),[pp.d,xn]);
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46 c = reshape (pp.P(:,1), pp.n, prod (pp.d));
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47 yi = reshape (c(idx,:).', [pp.d, xn]);
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48 for i = 2 : pp.k;
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49 c = reshape (pp.P(:,i), pp.n, prod (pp.d));
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50 yi = yi .* dx + reshape (c(idx,:).', [pp.d, xn]);
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51 endfor
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52 if (transposed && isscalar (pp.d) && pp.d == 1)
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53 yi = yi.';
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54 endif
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55 endif
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56 endfunction