Feature/box plot in comparer collection

modelskill/comparison/_collection_plotter.py

@@ -28,6 +28,7 @@ class ComparerCollectionPlotter:
     >>> cc.plot.hist()
     >>> cc.plot.kde()
     >>> cc.plot.taylor()
+    >>> cc.plot.box()
     """
 
     def __init__(self, cc: ComparerCollection) -> None:
@@ -535,3 +536,61 @@ def taylor(
             normalize_std=normalize_std,
             title=title,
         )
+
+    def box(self, *, ax=None, figsize=None, title=None, **kwargs) -> Axes:
+        """Plot box plot of observations and model data.
+
+        Parameters
+        ----------
+        ax : Axes, optional
+            matplotlib axes, by default None
+        figsize : tuple, optional
+            width and height of the figure, by default None
+        title : str, optional
+            plot title, by default None
+        **kwargs
+            passed to pandas.DataFrame.plot.box()
+
+        Returns
+        -------
+        Axes
+            matplotlib axes
+
+        Examples
+        --------
+        >>> cc.plot.box()
+        >>> cc.plot.box(showmeans=True)
+        >>> cc.plot.box(ax=ax, title="Box plot")
+        """
+        _, ax = _get_fig_ax(ax, figsize)
+
+        df = self.cc._to_long_dataframe()
+
+        unique_obs_cols = ["time", "x", "y", "observation"]
+        df = df.set_index(unique_obs_cols)
+        unique_obs_values = df[~df.duplicated()].obs_val.values
+
+        data = {"Observation": unique_obs_values}
+        for model in df.model.unique():
+            df_model = df[df.model == model]
+            data[model] = df_model.mod_val.values
+
+        data = {k: pd.Series(v) for k, v in data.items()}
+        df = pd.DataFrame(data)
+
+        if "grid" not in kwargs:
+            kwargs["grid"] = True
+
+        ax = df.plot.box(ax=ax, **kwargs)
+
+        ax.set_ylabel(f"{self.cc._unit_text}")
+
+        title = (
+            _default_univarate_title("Box plot", self.cc) if title is None else title
+        )
+        ax.set_title(title)
+
+        if self.is_directional:
+            _ytick_directional(ax)
+
+        return ax

tests/test_comparercollection.py

@@ -497,6 +497,7 @@ def test_plots_directional(cc):
         "kde",
         "hist",
         "taylor",
+        "box",
     ]
 )
 def cc_plot_function(cc, request):