Mercurial > octave-nkf

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

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
[project @ 2006-05-19 06:53:31 by jwe]
author jwe
date Fri, 19 May 2006 06:53:31 +0000
parents
children 34f96dd5441b
comparison
equal deleted inserted replaced
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{pp} = } mkpp (@var{x}, @var{p})
22 ## @deftypefnx {Function File} {@var{pp} = } mkpp (@var{x}, @var{p}, @var{d})
23 ##
24 ## Construct a piece-wise polynomial structure from sample points
25 ## @var{x} and coefficients @var{p}. The ith row of @var{p},
26 ## @code{@var{p} (@var{i},:)}, contains the coefficients for the polynomial
27 ## over the @var{i}-th interval, ordered from highest to
28 ## lowest. There must be one row for each interval in @var{x}, so
29 ## @code{rows (@var{p}) == length (@var{x}) - 1}.
30 ##
31 ## You can concatenate multiple polynomials of the same order over the
32 ## same set of intervals using @code{@var{p} = [ @var{p1}; @var{p2};
33 ## @dots{}; @var{pd} ]}. In this case, @code{rows (@var{p}) == @var{d}
34 ## * (length (@var{x}) - 1)}.
35 ##
36 ## @var{d} specifies the shape of the matrix @var{p} for all except the
37 ## last dimension. If @var{d} is not specified it will be computed as
38 ## @code{round (rows (@var{p}) / (length (@var{x}) - 1)) instead.
39 ##
40 ## @seealso{unmkpp, ppval, spline}
41 ## @end deftypefn
42
43 function pp = mkpp (x, P, d)
44 if (nargin < 2 || nargin > 3)
45 usage ("pp = mkpp(x,P,d)");
46 endif
47 pp.x = x(:);
48 pp.P = P;
49 pp.n = length (x) - 1;
50 pp.k = columns (P);
51 if (nargin < 3)
52 d = round (rows (P) / pp.n);
53 endif
54 pp.d = d;
55 if (pp.n*d != rows (P))
56 error ("mkpp: num intervals in x doesn't match num polynomials in P");
57 endif
58 endfunction
59
60 %!demo # linear interpolation
61 %! x=linspace(0,pi,5)';
62 %! t=[sin(x),cos(x)];
63 %! m=diff(t)./(x(2)-x(1));
64 %! b=t(1:4,:);
65 %! pp = mkpp(x, [m(:),b(:)]);
66 %! xi=linspace(0,pi,50);
67 %! plot(x,t,"x;control;",xi,ppval(pp,xi),";interp;");