fix: multiindex future warning

RELEASE_NOTES.rst

@@ -27,6 +27,8 @@ Upcoming Release
 * Fix regression when ``ExclusionContainer`` encounters a raster with an invalid CRS
   (https://github.com/PyPSA/atlite/pull/500).
 
+* Fix MultiIndex specific ``FutureWarning`` in ``convert_and_aggregate`` (https://github.com/PyPSA/atlite/pull/501).
+
 
 `v0.5.0 <https://github.com/PyPSA/atlite/releases/tag/v0.5.0>`__ (13th March 2026)
 =======================================================================================   

atlite/aggregate.py

@@ -5,25 +5,26 @@
 Functions for aggregating results.
 """
 
-import dask
+import scipy.sparse as sp
 import xarray as xr
+from dask.array.core import Array
 
 
-def aggregate_matrix(da, matrix, index):
-    if index.name is None:
-        index = index.rename("dim_0")
-    if isinstance(da.data, dask.array.core.Array):
+def aggregate_matrix(
+    da: xr.DataArray, matrix: sp.csr_matrix, coords: xr.Coordinates
+) -> xr.DataArray:
+    if isinstance(da.data, Array):
         da = da.stack(spatial=("y", "x"))
         da = da.chunk(dict(spatial=-1))
         return xr.apply_ufunc(
             lambda da: da * matrix.T,
             da,
             input_core_dims=[["spatial"]],
-            output_core_dims=[[index.name]],
+            output_core_dims=[list(coords.dims)],
             dask="parallelized",
             output_dtypes=[da.dtype],
-            dask_gufunc_kwargs=dict(output_sizes={index.name: index.size}),
-        ).assign_coords(**{index.name: index})
+            dask_gufunc_kwargs=dict(output_sizes=coords.sizes),
+        ).assign_coords(coords)
     else:
         da = da.stack(spatial=("y", "x")).transpose("spatial", "time")
-        return xr.DataArray(matrix * da, [index, da.coords["time"]])
+        return xr.DataArray(matrix * da, coords.assign(time=da.coords["time"]))

atlite/convert.py

@@ -40,6 +40,7 @@
     get_windturbineconfig,
     windturbine_smooth,
 )
+from atlite.utils import ensure_coords
 
 logger = logging.getLogger(__name__)
 
@@ -216,7 +217,7 @@ def convert_and_aggregate(
             )
 
         if isinstance(matrix, xr.DataArray):
-            coords = matrix.indexes.get(matrix.dims[1]).to_frame(index=False)
+            coords = matrix.indexes[matrix.dims[1]].to_frame(index=False)
             if not np.array_equal(coords[["x", "y"]], cutout.grid[["x", "y"]]):
                 raise ValueError(
                     "Matrix spatial coordinates not aligned with cutout spatial "
@@ -247,15 +248,17 @@ def convert_and_aggregate(
         else:
             matrix = csr_matrix(matrix) * spdiag(layout)
 
-    # From here on, matrix is defined and ensured to be a csr matrix.
-    if index is None:
-        index = pd.RangeIndex(matrix.shape[0])
+    # guaranteed by code flow above, helps type checker
+    assert isinstance(matrix, csr_matrix)
 
-    results = aggregate_matrix(da, matrix=matrix, index=index)
+    coords = ensure_coords(pd.RangeIndex(matrix.shape[0]) if index is None else index)
+    if len(coords.dims) > 1:
+        raise ValueError(f"index must have a single dimension, not: {coords.dims}")
+    results = aggregate_matrix(da, matrix=matrix, coords=coords)
 
     if per_unit or return_capacity:
         caps = matrix.sum(-1)
-        capacity = xr.DataArray(np.asarray(caps).flatten(), [index])
+        capacity = xr.DataArray(np.asarray(caps).flatten(), coords)
         capacity.attrs["units"] = "MW"
 
     if per_unit:

atlite/utils.py

@@ -19,6 +19,23 @@
 logger = logging.getLogger(__name__)
 
 
+def ensure_coords(index: pd.Index | xr.Coordinates) -> xr.Coordinates:
+    """
+    Convert an index or multiindex to coordinates
+    """
+    if isinstance(index, pd.MultiIndex):
+        coords = xr.Coordinates.from_pandas_multiindex(index, index.name or "dim_0")
+    elif isinstance(index, pd.Index):
+        coords = xr.Coordinates({index.name or "dim_0": index})
+    elif isinstance(index, xr.Coordinates):
+        coords = index
+    else:
+        raise ValueError(
+            f"index must be a pandas index or xarray coordinates, not: {index}"
+        )
+    return coords
+
+
 def migrate_from_cutout_directory(old_cutout_dir, path):
     """
     Convert an old style cutout directory to new style netcdf file.