Mercurial > octave-nkf
view scripts/polynomial/mkpp.m @ 20651:e54ecb33727e
lo-array-gripes.cc: Remove FIXME's related to buffer size.
* lo-array-gripes.cc: Remove FIXME's related to buffer size. Shorten sprintf
buffers from 100 to 64 characters (still well more than 19 required).
Use 'const' decorator on constant value for clarity. Remove extra space
between variable and array bracket.
author | Rik <rik@octave.org> |
---|---|
date | Mon, 12 Oct 2015 21:13:47 -0700 |
parents | aa36fb998a4d |
children |
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## Copyright (C) 2000-2015 Paul Kienzle ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} {@var{pp} =} mkpp (@var{breaks}, @var{coefs}) ## @deftypefnx {Function File} {@var{pp} =} mkpp (@var{breaks}, @var{coefs}, @var{d}) ## ## Construct a piecewise polynomial (pp) structure from sample points ## @var{breaks} and coefficients @var{coefs}. ## ## @var{breaks} must be a vector of strictly increasing values. The number of ## intervals is given by @code{@var{ni} = length (@var{breaks}) - 1}. ## ## When @var{m} is the polynomial order @var{coefs} must be of size: ## @var{ni} x @var{m} + 1. ## ## The i-th row of @var{coefs}, @code{@var{coefs} (@var{i},:)}, contains the ## coefficients for the polynomial over the @var{i}-th interval, ordered from ## highest (@var{m}) to lowest (@var{0}). ## ## @var{coefs} may also be a multi-dimensional array, specifying a vector-valued ## or array-valued polynomial. In that case the polynomial order is defined ## by the length of the last dimension of @var{coefs}. The size of first ## dimension(s) are given by the scalar or vector @var{d}. If @var{d} is not ## given it is set to @code{1}. In any case @var{coefs} is reshaped to a 2-D ## matrix of size @code{[@var{ni}*prod(@var{d} @var{m})] } ## ## @seealso{unmkpp, ppval, spline, pchip, ppder, ppint, ppjumps} ## @end deftypefn function pp = mkpp (x, P, d) ## check number of arguments if (nargin < 2 || nargin > 3) print_usage (); endif ## check x if (length (x) < 2) error ("mkpp: at least one interval is needed"); endif if (! isvector (x)) error ("mkpp: x must be a vector"); endif len = length (x) - 1; dP = length (size (P)); pp = struct ("form", "pp", "breaks", x(:).', "coefs", [], "pieces", len, "order", prod (size (P)) / len, "dim", 1); if (nargin == 3) pp.dim = d; pp.order /= prod (d); endif dim_vec = [pp.pieces * prod(pp.dim), pp.order]; pp.coefs = reshape (P, dim_vec); endfunction %!demo # linear interpolation %! x = linspace (0,pi,5)'; %! t = [sin(x), cos(x)]; %! m = diff (t) ./ (x(2)-x(1)); %! b = t(1:4,:); %! pp = mkpp (x, [m(:),b(:)]); %! xi = linspace (0,pi,50); %! plot (x,t,"x", xi,ppval (pp,xi)); %! legend ("control", "interp"); %!shared b,c,pp %! b = 1:3; c = 1:24; pp = mkpp (b,c); %!assert (pp.pieces, 2) %!assert (pp.order, 12) %!assert (pp.dim, 1) %!assert (size (pp.coefs), [2,12]) %! pp = mkpp (b,c,2); %!assert (pp.pieces, 2) %!assert (pp.order, 6) %!assert (pp.dim, 2) %!assert (size (pp.coefs), [4,6]) %! pp = mkpp (b,c,3); %!assert (pp.pieces, 2) %!assert (pp.order, 4) %!assert (pp.dim, 3) %!assert (size (pp.coefs), [6,4]) %! pp = mkpp (b,c,[2,3]); %!assert (pp.pieces, 2) %!assert (pp.order, 2) %!assert (pp.dim, [2,3]) %!assert (size (pp.coefs), [12,2])