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comparison scripts/polynomial/ppval.m @ 5824:448f9982e7fb

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[project @ 2006-05-19 06:53:31 by jwe]
author jwe
date Fri, 19 May 2006 06:53:31 +0000
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5823:080c08b192d8 5824:448f9982e7fb
1 ## Copyright (C) 2000 Paul Kienzle
2 ##
3 ## This file is part of Octave.
4 ##
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 2, or (at your option)
8 ## any later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, write to the Free
17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 ## 02110-1301, USA.
19
20 ## -*- texinfo -*-
21 ## @deftypefn {Function File} {@var{yi} =} ppval (@var{pp, @var{xi})
22 ##
23 ## Evaluate piece-wise polynomial @var{pp} at the points @var{xi}.
24 ## If @code{@var{pp}.d} is a scalar greater than 1, or an array,
25 ## then the returned value @var{yi} will be an array that is
26 ## @code{d1, d1, @dots{}, dk, length (@var{xi})]}.
27 ##
28 ## @seealso{mkpp, unmkpp, spline}
29 ## @end deftypefn
30
31 function yi = ppval (pp, xi)
32
33 if (nargin != 2)
34 usage ("yi = ppval(pp, xi)")
35 endif
36 if (! isstruct (pp))
37 error ("ppval: expects a pp structure");
38 endif
39 if (isempty (xi))
40 yi = [];
41 else
42 transposed = (columns (xi) == 1);
43 xi = xi(:);
44 xn = length (xi);
45 idx = lookup (pp.x(2:pp.n), xi) + 1;
46 dx = (xi - pp.x(idx))';
47 dx = reshape (dx(ones(1,prod(pp.d)),:),[pp.d,xn]);
48 c = reshape (pp.P(:,1), pp.n, prod (pp.d));
49 yi = reshape (c(idx,:)', [pp.d, xn]);
50 for i = 2 : pp.k;
51 c = reshape (pp.P(:,i), pp.n, prod (pp.d));
52 yi = yi .* dx + reshape (c(idx,:)', [pp.d, xn]);
53 endfor
54 if (transposed && isscalar (pp.d) && pp.d == 1)
55 yi = yi.';
56 endif
57 endif
58 endfunction