--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/splines/spline.m	Wed Oct 10 19:54:49 2001 +0000
@@ -0,0 +1,59 @@
+## 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, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{pp} = } spline (@var{x}, @var{y})
+## @deftypefnx {Function File} {@var{yi} = } spline (@var{x}, @var{y}, @var{xi})
+## cubic spline interpolation
+##
+## @seealso{ppval, csapi, csape}
+## @end deftypefn
+
+
+## Author:  Kai Habel <kai.habel@gmx.de>
+## Date: 3. dec 2000
+## 2001-02-08 Paul Kienzle
+##   * copied from csapi.m
+
+function ret = spline (x, y, xi)
+
+  ret = csape (x, y, 'not-a-knot');
+
+  if (nargin == 3)
+    ret = ppval (ret, xi);
+  endif
+
+endfunction
+
+%!demo
+%! x = 0:10; y = sin(x);
+%! xspline = 0:0.1:10; yspline = spline(x,y,xspline);
+%! title("spline fit to points from sin(x)");
+%! plot(xspline,sin(xspline),";original;",...
+%!      xspline,yspline,"-;interpolation;",...
+%!      x,y,"+;interpolation points;");
+%! %--------------------------------------------------------
+%! % confirm that interpolated function matches the original
+
+%!shared x,y
+%! x = [0:10]'; y = sin(x);
+%!assert (spline(x,y,x), y);
+%!assert (spline(x,y,x'), y');
+%!assert (spline(x',y',x'), y');
+%!assert (spline(x',y',x), y);
+%!assert (isempty(spline(x',y',[])));
+%!assert (isempty(spline(x,y,[])));
+%!assert (spline(x,[y,y],x), [spline(x,y,x),spline(x,y,x)])