--- /dev/null
+## Copyright (C) 2010 Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope 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.
+##
+## LTI Syncope 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 LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## Number of outputs and inputs of transfer function numerator and
+## denominator. For internal use only.
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: February 2010
+## Version: 0.1
+
+function [p, m, l] = __frd_dim__ (H, w)
+
+ if (! isnumeric (H))
+ error ("frd: H must be a 3-dimensional numeric array");
+ endif
+
+ lw = length (w);
+
+ if (! isempty (w) && (! is_real_vector (w) || any (w < 0) \
+ || ! issorted (w) || w(1) > w(end) \
+ || length (unique (w)) != lw))
+ error ("frd: w must be a vector of positive real numbers in ascending order");
+ endif
+
+ [p, m, l] = size (H);
+
+ if (l != lw)
+ error ("frd: H (%dx%dx%d) and w (%d) must have equal length",
+ p, m, l, lw);
+ endif
+
+endfunction