Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / splines-1.0.7 / fnder.m

diff --git a/octave_packages/splines-1.0.7/fnder.m b/octave_packages/splines-1.0.7/fnder.m
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+## Copyright (C) 2000  Kai Habel
+##
+## This program 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 2 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 program; If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} { } fnder (@var{pp}, @var{order})
+## differentiate the spline in pp-form 
+##
+## @seealso{ppval}
+## @end deftypefn
+
+## Author:  Kai Habel <kai.habel@gmx.de>
+## Date: 20. feb 2001
+
+function dpp = fnder (pp, o)
+
+  if (nargin < 1 || nargin > 2)
+    usage ("fnder (pp [, order])");
+  endif
+  if (nargin < 2)
+    o = 1;
+  endif
+
+  [X, P, N, K, D] = unmkpp (pp);
+  c = columns (P);
+  r = rows (P);
+
+  for i = 1:o
+    #pp.P = polyder (pp.P); matrix capable polyder is needed.
+    P = P(:, 1:c - 1) .* kron ((c - 1):- 1:1, ones (r,1));
+  endfor
+
+  dpp = mkpp (X, P);
+
+endfunction