def rank(self, dim, pct=False, keep_attrs=None):
        """Ranks the data.

        Equal values are assigned a rank that is the average of the ranks that
        would have been otherwise assigned to all of the values within that
        set.  Ranks begin at 1, not 0. If pct, computes percentage ranks.

        NaNs in the input array are returned as NaNs.

        The `bottleneck` library is required.

        Parameters
        ----------
        dim : str
            Dimension over which to compute rank.
        pct : bool, optional
            If True, compute percentage ranks, otherwise compute integer ranks.
        keep_attrs : bool, optional
            If True, the dataset's attributes (`attrs`) will be copied from
            the original object to the new one.  If False (default), the new
            object will be returned without attributes.

        Returns
        -------
        ranked : DataArray
            DataArray with the same coordinates and dtype 'float64'.

        Examples
        --------

        >>> arr = xr.DataArray([5, 6, 7], dims='x')
        >>> arr.rank('x')
        <xarray.DataArray (x: 3)>
        array([ 1.,   2.,   3.])
        Dimensions without coordinates: x
        """

        ds = self._to_temp_dataset().rank(dim, pct=pct, keep_attrs=keep_attrs)
        return self._from_temp_dataset(ds)