Added overloaded isempty function for dynSeries class.

matlab/@dynSeries/isempty.m

+function b = isempty(A)
+%@info:
+%! @deftypefn {Function File} {@var{b} =} isempty (@var{A})
+%! @anchor{@dynSeries/isempty}
+%! @sp 1
+%! Overloads the isempty function for the Dynare time series class (@ref{dynSeries}).
+%! @sp 2
+%! @strong{Inputs}
+%! @sp 1
+%! @table @ @var
+%! @item 1
+%! Dynare time series object instantiated by @ref{dynSeries}.
+%! @end table
+%! @sp 1
+%! @strong{Outputs}
+%! @sp 1
+%! @table @ @var
+%! @item b
+%! Scalar integer (0 or 1).
+%! @end deftypefn
+%@eod:
+
+% Copyright (C) 2011, 2012 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/>.
+
+% AUTHOR(S) stephane DOT adjemian AT univ DASH lemans DOT fr
+    
+b = isempty(A.data) && isequal(A.nobs,0) && isequal(A.vobs,0);
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