Skip coords with scalar value (#868)

pymc_marketing/mmm/plot.py

@@ -22,6 +22,8 @@
 import numpy.typing as npt
 import xarray as xr
 
+from pymc_marketing.mmm.utils import drop_scalar_coords
+
 Values = Sequence[Any] | npt.NDArray[Any]
 Coords = dict[str, Values]
 
@@ -100,6 +102,8 @@ def plot_hdi(
         Figure and the axes
 
     """
+    curve = drop_scalar_coords(curve)
+
     hdi_kwargs = hdi_kwargs or {}
     conf = az.hdi(curve, **hdi_kwargs)[curve.name]
 
@@ -190,6 +194,8 @@ def plot_samples(
         Figure and the axes
 
     """
+    curve = drop_scalar_coords(curve)
+
     plot_coords = get_plot_coords(
         curve.coords,
         non_grid_names=non_grid_names.union({"chain", "draw"}),
@@ -262,6 +268,7 @@ def plot_curve(
         Figure and the axes
 
     """
+    curve = drop_scalar_coords(curve)
 
     hdi_kwargs = hdi_kwargs or {}
     sample_kwargs = sample_kwargs or {}

pymc_marketing/mmm/utils.py

@@ -361,3 +361,30 @@ def create_new_spend_data(
             spend,
         ]
     )
+
+
+def drop_scalar_coords(curve: xr.DataArray) -> xr.DataArray:
+    """
+    Remove scalar coordinates from an xarray DataArray.
+
+    This function identifies and removes scalar coordinates from the given
+    DataArray. Scalar coordinates are those with a single value that are
+    not part of the DataArray's indexes. The function returns a new DataArray
+    with the scalar coordinates removed.
+
+    Parameters
+    ----------
+    curve : xr.DataArray
+        The input DataArray from which scalar coordinates will be removed.
+
+    Returns
+    -------
+    xr.DataArray
+        A new DataArray with the identified scalar coordinates removed.
+    """
+    scalar_coords_to_drop = []
+    for coord, values in curve.coords.items():
+        if values.size == 1 and coord not in curve.indexes:
+            scalar_coords_to_drop.append(coord)
+
+    return curve.reset_coords(scalar_coords_to_drop, drop=True)

tests/mmm/test_utils.py

@@ -21,6 +21,7 @@
     apply_sklearn_transformer_across_dim,
     compute_sigmoid_second_derivative,
     create_new_spend_data,
+    drop_scalar_coords,
     estimate_menten_parameters,
     estimate_sigmoid_parameters,
     find_sigmoid_inflection_point,
@@ -281,3 +282,34 @@ def test_create_new_spend_data_value_errors() -> None:
             one_time=True,
             spend_leading_up=np.array([3, 4, 5]),
         )
+
+
+@pytest.fixture
+def mock_curve_with_scalars() -> xr.DataArray:
+    coords = {
+        "x": [1, 2, 3],
+        "y": [10, 20, 30],
+        "scalar1": 42,  # Scalar coordinate
+        "scalar2": 3.14,  # Another scalar coordinate
+    }
+    data = np.random.rand(3, 3)
+    return xr.DataArray(data, coords=coords, dims=["x", "y"])
+
+
+def test_drop_scalar_coords(mock_curve_with_scalars) -> None:
+    original_curve = mock_curve_with_scalars.copy(deep=True)  # Make a deep copy
+    curve = drop_scalar_coords(mock_curve_with_scalars)
+
+    # Ensure scalar coordinates are removed
+    assert "scalar1" not in curve.coords
+    assert "scalar2" not in curve.coords
+
+    # Ensure other coordinates are still present
+    assert "x" in curve.coords
+    assert "y" in curve.coords
+
+    # Ensure data shape is unchanged
+    assert curve.shape == (3, 3)
+
+    # Ensure the original DataArray was not modified
+    xr.testing.assert_identical(mock_curve_with_scalars, original_curve)