plot_hdi: add exception if x is type np.datetime64 and `smooth=Tr…

…ue` (#2016)

* add exception if x is type np.datetime64 in plot_hdi

* updated tests for plot_hdi

* updated changelog

* fixed test

* added y and hdi_data to test

* fixed pylint error

* run black

Co-authored-by: Agustina Arroyuelo <agustinaarroyuelo@gmail.com>

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### New features
 
 ### Maintenance and fixes
+* Add exception in `az.plot_hdi` for `x` of type `np.datetime64` and `smooth=True` ([2016](https://github.com/arviz-devs/arviz/pull/2016))
 
 ### Deprecation
 

arviz/plots/hdiplot.py

@@ -164,6 +164,9 @@ def plot_hdi(
         raise TypeError(msg.format(x_shape, hdi_shape))
 
     if smooth:
+        if isinstance(x[0], np.datetime64):
+            raise TypeError("Cannot deal with x as type datetime. Recommend setting smooth=False.")
+
         if smooth_kwargs is None:
             smooth_kwargs = {}
         smooth_kwargs.setdefault("window_length", 55)

arviz/tests/base_tests/test_plots_matplotlib.py

@@ -1192,6 +1192,15 @@ def test_plot_hdi_dataset_error(models):
         plot_hdi(np.arange(8), hdi_data=hdi_data)
 
 
+def test_plot_hdi_datetime_error():
+    """Check x as datetime raises an error."""
+    x_data = np.arange(start="2022-01-01", stop="2022-03-01", dtype=np.datetime64)
+    y_data = np.random.normal(0, 5, (1, 200, x_data.shape[0]))
+    hdi_data = hdi(y_data)
+    with pytest.raises(TypeError, match="Cannot deal with x as type datetime."):
+        plot_hdi(x=x_data, y=y_data, hdi_data=hdi_data)
+
+
 @pytest.mark.parametrize("limits", [(-10.0, 10.0), (-5, 5), (None, None)])
 def test_kde_scipy(limits):
     """