Added @dynSeries/lag method.

matlab/@dynSeries/lag.m

+function us = lag(ts,p)
+
+%@info:
+%! @deftypefn {Function File} {@var{us} =} lag (@var{ts})
+%! @anchor{lag}
+%! @sp 1
+%! Computes lagged time series.
+%! @sp 2
+%! @strong{Inputs}
+%! @sp 1
+%! @table @var
+%! @item ts
+%! Dynare time series object, instantiated by @ref{dynSeries}
+%! @end table
+%! @sp 2
+%! @strong{Outputs}
+%! @sp 1
+%! @table @var
+%! @item us
+%! Dynare time series object with transformed data field.
+%! @end table
+%! @end deftypefn
+%@eod:
+
+% Copyright (C) 2013 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/>.
+
+% Set default number of lags
+if nargin<2
+    p = 1;
+end
+
+% Copy of ts dynSeries object
+us = ts;
+
+% Update data member
+us.data = [NaN(p,ts.vobs);  ts.data(1:end-p,:)];
+
+for i=1:ts.vobs
+    us.name(i) = {[ 'lag(' ts.name{i} ',' int2str(p) ')']};
+    us.tex(i) = {[ ts.tex{i} '_{-' int2str(p) '}']};
+end
+
+%@test:1
+%$ t = zeros(4,1);
+%$
+%$ try
+%$     data = transpose(0:1:50);
+%$     ts = dynSeries(data,'1950Q1');
+%$     a = ts.lag;
+%$     b = ts.lag.lag;
+%$     c = lag(ts,2);
+%$     t(1) = 1;
+%$ catch
+%$     t = 0;
+%$ end
+%$
+%$ if length(t)>1
+%$     DATA = [NaN(1,ts.vobs); transpose(0:1:49)];
+%$     t(2) = dyn_assert(a.data,DATA,1e-15);
+%$     DATA = [NaN(2,ts.vobs); transpose(0:1:48)];
+%$     t(3) = dyn_assert(b.data,DATA,1e-15);
+%$     t(4) = dyn_assert(b.data,c.data,1e-15);
+%$ end
+%$
+%$ T = all(t);
+%@eof:1b
\ No newline at end of file

matlab/@dynSeries/subsref.m

@@ -66,7 +66,7 @@ switch S(1).type
     switch S(1).subs
       case {'data','nobs','vobs','name','tex','freq','time','init'}        % Public members.
         B = builtin('subsref', A, S(1));
-      case {'log','exp','ygrowth','qgrowth','ydiff','qdiff'}               % Give "dot access" to public methods.
+      case {'log','exp','ygrowth','qgrowth','ydiff','qdiff','lag'}         % Give "dot access" to public methods.
         B = feval(S(1).subs,A);
       case {'save'}                                                        % Save dynSeries object on disk (default is a csv file). 
         B = NaN;