def _map_to_memory(self, stride=1):
        r"""Maps results to memory. Will be stored in attribute :attr:`_Y`."""
        self._mapping_to_mem_active = True
        try:
            self._Y = self.get_output(stride=stride)
            from pyemma.coordinates.data import DataInMemory
            self._Y_source = DataInMemory(self._Y)
        finally:
            self._mapping_to_mem_active = False

        self._in_memory = True