update packages

[CreaPhase.git] / octave_packages / m / polynomial / ppder.m

diff --git a/octave_packages/m/polynomial/ppder.m b/octave_packages/m/polynomial/ppder.m
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+## Copyright (C) 2008-2012 VZLU Prague, a.s., Czech Republic
+##
+## 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.
+##
+## This program 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 this software; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {ppd =} ppder (pp)
+## @deftypefnx {Function File} {ppd =} ppder (pp, m)
+## Compute the piecewise @var{m}-th derivative of a piecewise polynomial
+## struct @var{pp}.  If @var{m} is omitted the first derivative is calculated.
+## @seealso{mkpp, ppval, ppint}
+## @end deftypefn
+
+function ppd = ppder (pp, m)
+
+  if ((nargin < 1) || (nargin > 2))
+    print_usage ();
+  elseif (nargin == 1)
+    m = 1;
+  endif
+
+  if (! (isstruct (pp) && strcmp (pp.form, "pp")))
+    error ("ppder: PP must be a structure");
+  endif
+
+  [x, p, n, k, d] = unmkpp (pp);
+
+  if (k - m <= 0)
+    x = [x(1) x(end)];
+    pd = zeros (prod (d), 1);
+  else
+    f = k : -1 : 1;
+    ff = bincoeff (f, m + 1) .* factorial (m + 1) ./ f;
+    k -= m;
+    pd = p(:,1:k) * diag (ff(1:k));
+  endif
+
+  ppd = mkpp (x, pd, d);
+endfunction
+
+%!shared x,y,pp,ppd
+%! x=0:8;y=[x.^2;x.^3+1];pp=spline(x,y);
+%! ppd=ppder(pp);
+%!assert(ppval(ppd,x),[2*x;3*x.^2],1e-14)
+%!assert(ppd.order,3)
+%! ppd=ppder(pp,2);
+%!assert(ppval(ppd,x),[2*ones(size(x));6*x],1e-14)
+%!assert(ppd.order,2)
+%! ppd=ppder(pp,3);
+%!assert(ppd.order,1)
+%!assert(ppd.pieces,8)
+%!assert(size(ppd.coefs),[16,1])
+%! ppd=ppder(pp,4);
+%!assert(ppd.order,1)
+%!assert(ppd.pieces,1)
+%!assert(size(ppd.coefs),[2,1])
+%!assert(ppval(ppd,x),zeros(size(y)),1e-14)