Added flip method.

src/@dseries/flip.m

+function o = flip(o) % --*-- Unitary tests --*--
+
+% Flips the rows in the data member (without changing the
+% periods order)
+%
+% INPUTS
+% - o [dseries]
+%
+% OUTPUTS
+% - o [dseries]
+
+% Copyright © 2020 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/>.
+
+o = copy(o);
+o.flip_;
+
+return
+%@test:1
+% Define a dates object
+data = transpose(1:3);
+o = dseries(data);
+q = dseries(data);
+
+% Call the tested routine.
+try
+    p = o.flip();
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+     t(2) = dassert(o, q);
+     t(3) = dassert(p.data, [3; 2; 1]);
+end
+
+T = all(t);
+%@eof:1
\ No newline at end of file

src/@dseries/flip_.m

+function o = flip_(o) % --*-- Unitary tests --*--
+
+% Flips the rows in the data member (without changing the
+% periods order)
+%
+% INPUTS
+% - o [dseries]
+%
+% OUTPUTS
+% - o [dseries]
+
+% Copyright © 2020 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/>.
+
+for i=1:vobs(o)
+    if isempty(o.ops{i})
+        o.ops(i) = {['flip(' o.name{i} ')']};
+    else
+        o.ops(i) = {['flip(' o.ops{i} ')']};
+    end
+end
+
+o.data = flip(o.data);
+
+return
+%@test:1
+% Define a dates object
+data = [transpose(1:3) transpose(4:6)];
+o = dseries(data);
+q = o;
+r = copy(o);
+
+% Call the tested routine.
+try
+    o.flip_();
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+     t(2) = dassert(o.data, [3 6; 2 5; 1 4]);
+     t(3) = dassert(q.data, [3 6; 2 5; 1 4]);
+     t(4) = dassert(r.data, data);
+     t(5) = dassert(o.name{1}, 'Variable_1') && dassert(o.name{2}, 'Variable_2');
+     t(6) = dassert(q.name{1}, 'Variable_1') && dassert(q.name{2}, 'Variable_2');
+     t(7) = dassert(r.name{1}, 'Variable_1') && dassert(r.name{2}, 'Variable_2');
+     t(8) = dassert(o.ops{1}, 'flip(Variable_1)') && dassert(o.ops{2}, 'flip(Variable_2)');
+     t(9) = dassert(q.ops{1}, 'flip(Variable_1)') && dassert(q.ops{2}, 'flip(Variable_2)');
+end
+
+T = all(t);
+%@eof:1
+
+%@test:2
+%$ % Define a dates object
+%$ data = [ones(10,1), -ones(10,1)];
+%$ o = dseries(data);
+%$ q = o;
+%$ r = copy(o);
+%$
+%$ % Call the tested routine.
+%$ try
+%$     o.abs_();
+%$     t(1) = true;
+%$ catch
+%$     t(1) = false;
+%$ end
+%$
+%$ if t(1)
+%$      t(2) = dassert(length(o.name), 2);
+%$      t(3) = dassert(o.name{1},'Variable_1');
+%$      t(4) = dassert(o.name{2},'Variable_2');
+%$      t(5) = dassert(q.name{1},'Variable_1');
+%$      t(6) = dassert(q.name{2},'Variable_2');
+%$      t(7) = dassert(r.name{1},'Variable_1');
+%$      t(8) = dassert(r.name{2},'Variable_2');
+%$      t(9) = dassert(o.ops{1},'abs(Variable_1)');
+%$      t(10) = dassert(o.ops{2},'abs(Variable_2)');
+%$      t(11) = dassert(q.ops{1},'abs(Variable_1)');
+%$      t(12) = dassert(q.ops{2},'abs(Variable_2)');
+%$      t(13) = isempty(r.ops{1});
+%$      t(14) = isempty(r.ops{2});
+%$ end
+%$
+%$ T = all(t);
+%@eof:2
\ No newline at end of file

src/@dseries/subsref.m

@@ -116,6 +116,7 @@ switch S(1).type
             'diff', 'diff_', ...
             'mdiff','mdiff_', ...
             'abs','abs_', ...
+            'flip','flip_', ...
             'isnan', ...
             'isinf', ...
             'isreal', ...