Method set_index

xarray/core/dataset.py:4725–4888

Set Dataset (multi-)indexes using one or more existing coordinates or variables. This legacy method is limited to pandas (multi-)indexes and 1-dimensional "dimension" coordinates. See :py:meth:`~Dataset.set_xindex` for setting a pandas or a custom Xarray-comp

(
        self,
        indexes: Mapping[Any, Hashable | Sequence[Hashable]] | None = None,
        append: bool = False,
        **indexes_kwargs: Hashable | Sequence[Hashable],
    )

        )

    def set_index(
        self,
        indexes: Mapping[Any, Hashable | Sequence[Hashable]] | None = None,
        append: bool = False,
        **indexes_kwargs: Hashable | Sequence[Hashable],
    ) -> Self:
        """Set Dataset (multi-)indexes using one or more existing coordinates
        or variables.

        This legacy method is limited to pandas (multi-)indexes and
        1-dimensional "dimension" coordinates. See
        :py:meth:`~Dataset.set_xindex` for setting a pandas or a custom
        Xarray-compatible index from one or more arbitrary coordinates.

        Parameters
        ----------
        indexes : {dim: index, ...}
            Mapping from names matching dimensions and values given
            by (lists of) the names of existing coordinates or variables to set
            as new (multi-)index.
        append : bool, default: False
            If True, append the supplied index(es) to the existing index(es).
            Otherwise replace the existing index(es) (default).
        **indexes_kwargs : optional
            The keyword arguments form of ``indexes``.
            One of indexes or indexes_kwargs must be provided.

        Returns
        -------
        obj : Dataset
            Another dataset, with this dataset's data but replaced coordinates.

        Examples
        --------
        >>> arr = xr.DataArray(
        ...     data=np.ones((2, 3)),
        ...     dims=["x", "y"],
        ...     coords={"x": range(2), "y": range(3), "a": ("x", [3, 4])},
        ... )
        >>> ds = xr.Dataset({"v": arr})
        >>> ds
        <xarray.Dataset> Size: 104B
        Dimensions:  (x: 2, y: 3)
        Coordinates:
          * x        (x) int64 16B 0 1
            a        (x) int64 16B 3 4
          * y        (y) int64 24B 0 1 2
        Data variables:
            v        (x, y) float64 48B 1.0 1.0 1.0 1.0 1.0 1.0
        >>> ds.set_index(x="a")
        <xarray.Dataset> Size: 88B
        Dimensions:  (x: 2, y: 3)
        Coordinates:
          * x        (x) int64 16B 3 4
          * y        (y) int64 24B 0 1 2
        Data variables:
            v        (x, y) float64 48B 1.0 1.0 1.0 1.0 1.0 1.0