Added the possibility to call rename method with one argument if dseries

object contains only one variable.

Also check that the dseries object is not empty.

src/@dseries/rename.m

@@ -17,15 +17,29 @@ function ts = rename(ts,old,new) % --*-- Unitary tests --*--
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
+if isempty(ts)
+    error('dseries::rename: Cannot rename variable(s) because the object is empty!')
+end
+
+if nargin<3
+    if isequal(vobs(ts), 1)
+        new = old;
+    else
+        error('dseries::rename: Missing argument!')
+    end
+    if ~ischar(new)
+        error(['dseries::rename: Input argument ''' inputname(2)  '''  has to be a string!'])
+    end
+    idname = 1;
+else
     if ~ischar(old) || ~ischar(new)
         error(['dseries::rename: Input arguments ''' inputname(2) ''' and ''' inputname(3) '''  have to be strings!'])
     end
-    
     idname = find(strcmp(old,ts.name));
-
     if isempty(idname)
         error(['dseries::rename: Variable ' old ' is unknown in dseries object ' inputname(1)  '!'])
     end
+end
 
 ts.name(idname) = {new};