dates.subsref: compatibility fix for MATLAB < R2010b

Provide an alternative implementation of ismatrix.

src/initialize_dseries_class.m

@@ -112,6 +112,10 @@ if ~exist('one_sided_hp_filter','file')
     p{end+1} = 'utilities/missing/one_sided_hp_filter';
 end
 
+if ~exist('ismatrix','file')
+    p{end+1} = 'utilities/missing/ismatrix';
+end
+
 % Set path
 P = cellfun(@(c)[dseries_src_root c], p, 'uni', false);
 addpath(P{:});

src/utilities/missing/ismatrix/ismatrix.m

+function r = ismatrix(V)
+% Copyright (C) 2018 Dynare Team
+%
+% This file is part of Dynare.
+%
+% Dynare 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.
+%
+% Dynare 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 Dynare.  If not, see <http://www.gnu.org/licenses/>.
+
+r = (ndims(V) == 2);