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## Copyright (C) 2000-2013 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{x}, @var{p}, @var{n}, @var{k}, @var{d}] =} unmkpp (@var{pp})
##
## Extract the components of a piecewise polynomial structure @var{pp}.
## The components are:
##
## @table @asis
## @item @var{x}
## Sample points.
##
## @item @var{p}
## Polynomial coefficients for points in sample interval. @code{@var{p}
## (@var{i}, :)} contains the coefficients for the polynomial over
## interval @var{i} ordered from highest to lowest. If @code{@var{d} >
## 1}, @code{@var{p} (@var{r}, @var{i}, :)} contains the coefficients for
## the r-th polynomial defined on interval @var{i}.
##
## @item @var{n}
## Number of polynomial pieces.
##
## @item @var{k}
## Order of the polynomial plus 1.
##
## @item @var{d}
## Number of polynomials defined for each interval.
## @end table
##
## @seealso{mkpp, ppval, spline, pchip}
## @end deftypefn
function [x, P, n, k, d] = unmkpp (pp)
if (nargin != 1)
print_usage ();
endif
if (! (isstruct (pp) && isfield (pp, "form") && strcmp (pp.form, "pp")))
error ("unmkpp: PP must be a piecewise polynomial structure");
endif
x = pp.breaks;
P = pp.coefs;
n = pp.pieces;
k = pp.order;
d = pp.dim;
endfunction
%!test
%! b = 1:3;
%! c = 1:24;
%! pp = mkpp (b,c);
%! [x, P, n, k, d] = unmkpp (pp);
%! assert (x, b);
%! assert (P, reshape (c, [2 12]));
%! assert (n, 2);
%! assert (k, 12);
%! assert (d, 1);
%% Test input validation
%!error unmkpp ()
%!error unmkpp (1,2)
%!error <piecewise polynomial structure> unmkpp (1)
%!error <piecewise polynomial structure> unmkpp (struct ("field1", "pp"))
%!error <piecewise polynomial structure> unmkpp (struct ("form", "not_a_pp"))
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