Fix interval labels with units

doc/whats-new.rst

@@ -68,6 +68,8 @@ Bug fixes
   By `Alessandro Amici <https://github.com/alexamici>`_
 - Limit number of data rows when printing large datasets. (:issue:`4736`, :pull:`4750`). By `Jimmy Westling <https://github.com/illviljan>`_.
 - Add ``missing_dims`` parameter to transpose (:issue:`4647`, :pull:`4767`). By `Daniel Mesejo <https://github.com/mesejo>`_.
+- Resolve intervals before appending other metadata to labels when plotting (:issue:`4322`, :pull:`4794`).
+  By `Justus Magin <https://github.com/keewis>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/plot/facetgrid.py

@@ -306,9 +306,11 @@ def map_dataarray_line(
                 )
                 self._mappables.append(mappable)
 
-        _, _, hueplt, xlabel, ylabel, huelabel = _infer_line_data(
+        xplt, yplt, hueplt, huelabel = _infer_line_data(
             darray=self.data.loc[self.name_dicts.flat[0]], x=x, y=y, hue=hue
         )
+        xlabel = label_from_attrs(xplt)
+        ylabel = label_from_attrs(yplt)
 
         self._hue_var = hueplt
         self._hue_label = huelabel

xarray/plot/plot.py

@@ -107,10 +107,7 @@ def _infer_line_data(darray, x, y, hue):
         huelabel = label_from_attrs(darray[huename])
         hueplt = darray[huename]
 
-    xlabel = label_from_attrs(xplt)
-    ylabel = label_from_attrs(yplt)
-
-    return xplt, yplt, hueplt, xlabel, ylabel, huelabel
+    return xplt, yplt, hueplt, huelabel
 
 
 def plot(
@@ -292,12 +289,14 @@ def line(
         assert "args" not in kwargs
 
     ax = get_axis(figsize, size, aspect, ax)
-    xplt, yplt, hueplt, xlabel, ylabel, hue_label = _infer_line_data(darray, x, y, hue)
+    xplt, yplt, hueplt, hue_label = _infer_line_data(darray, x, y, hue)
 
     # Remove pd.Intervals if contained in xplt.values and/or yplt.values.
-    xplt_val, yplt_val, xlabel, ylabel, kwargs = _resolve_intervals_1dplot(
-        xplt.values, yplt.values, xlabel, ylabel, kwargs
+    xplt_val, yplt_val, x_suffix, y_suffix, kwargs = _resolve_intervals_1dplot(
+        xplt.values, yplt.values, kwargs
     )
+    xlabel = label_from_attrs(xplt, extra=x_suffix)
+    ylabel = label_from_attrs(yplt, extra=y_suffix)
 
     _ensure_plottable(xplt_val, yplt_val)
 

xarray/plot/utils.py

@@ -503,12 +503,14 @@ def _interval_to_double_bound_points(xarray, yarray):
     return xarray, yarray
 
 
-def _resolve_intervals_1dplot(xval, yval, xlabel, ylabel, kwargs):
+def _resolve_intervals_1dplot(xval, yval, kwargs):
     """
     Helper function to replace the values of x and/or y coordinate arrays
     containing pd.Interval with their mid-points or - for step plots - double
     points which double the length.
     """
+    x_suffix = ""
+    y_suffix = ""
 
     # Is it a step plot? (see matplotlib.Axes.step)
     if kwargs.get("drawstyle", "").startswith("steps-"):
@@ -534,13 +536,13 @@ def _resolve_intervals_1dplot(xval, yval, xlabel, ylabel, kwargs):
         # Convert intervals to mid points and adjust labels
         if _valid_other_type(xval, [pd.Interval]):
             xval = _interval_to_mid_points(xval)
-            xlabel += "_center"
+            x_suffix = "_center"
         if _valid_other_type(yval, [pd.Interval]):
             yval = _interval_to_mid_points(yval)
-            ylabel += "_center"
+            y_suffix = "_center"
 
     # return converted arguments
-    return xval, yval, xlabel, ylabel, kwargs
+    return xval, yval, x_suffix, y_suffix, kwargs
 
 
 def _resolve_intervals_2dplot(val, func_name):

xarray/tests/test_plot.py

@@ -592,6 +592,20 @@ def test_coord_with_interval_xy(self):
         bins = [-1, 0, 1, 2]
         self.darray.groupby_bins("dim_0", bins).mean(...).dim_0_bins.plot()
 
+    @pytest.mark.parametrize("dim", ("x", "y"))
+    def test_labels_with_units_with_interval(self, dim):
+        """Test line plot with intervals and a units attribute."""
+        bins = [-1, 0, 1, 2]
+        arr = self.darray.groupby_bins("dim_0", bins).mean(...)
+        arr.dim_0_bins.attrs["units"] = "m"
+
+        (mappable,) = arr.plot(**{dim: "dim_0_bins"})
+        ax = mappable.figure.gca()
+        actual = getattr(ax, f"get_{dim}label")()
+
+        expected = "dim_0_bins_center [m]"
+        assert actual == expected
+
 
 class TestPlot1D(PlotTestCase):
     @pytest.fixture(autouse=True)