Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / optim-1.2.0 / private / __s2mat__.m

diff --git a/octave_packages/optim-1.2.0/private/__s2mat__.m b/octave_packages/optim-1.2.0/private/__s2mat__.m
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+## Copyright (C) 2010 Olaf Till <olaf.till@uni-jena.de>
+##
+## 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 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 program; If not, see <http://www.gnu.org/licenses/>.
+
+## __s2mat__ (s, ord)
+##
+## Returns a matrix of second derivatives with respect to some
+## parameters from the structure-based representation of such a matrix
+## in s, using the order of parameter names ord. s has to contain all
+## fields named in ord. Each field has some subfields named in ord so
+## that each second derivative is represented at least in one of its two
+## possible orders. If it is represented differently in both orders, no
+## error is returned, but both entries might get into the final matrix
+## at symmetric positions.
+##
+## Should be included as a subfunction of a wrapper for optimization
+## functions possibly needing a Hessian.
+
+function ret = __s2mat__ (s, ord)
+
+  if (any (size (s) != [1, 1]))
+    error ("structure must be scalar");
+  endif
+
+  if (! (iscell (ord) && isvector (ord)))
+    error ("ord must be a one-dimensional cell-array");
+  endif
+
+  c = fields2cell (structcat (1, fields2cell (s, ord){:}), ord);
+
+  neidx = ! (eidx = cellfun ("isempty", c));
+
+  ret = zeros (length (ord));
+
+  ret(neidx) = [c{neidx}]; # faster than [c{:}] ?
+
+  ret(eidx) = ret.'(eidx);
+
+endfunction
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