feat: new "band" histtype

Author: andrzejnovak

src/mplhep/plot.py

@@ -152,7 +152,7 @@ def histplot(
             raise ValueError("ax must be a matplotlib Axes object")
 
     # arg check
-    _allowed_histtype = ["fill", "step", "errorbar"]
+    _allowed_histtype = ["fill", "step", "errorbar", "band"]
     _err_message = f"Select 'histtype' from: {_allowed_histtype}"
     assert histtype in _allowed_histtype, _err_message
     assert flow is None or flow in {
@@ -462,6 +462,23 @@ def iterable_not_string(arg):
             return_artists.append(StairsArtists(_f, None, None))
         _artist = _f
 
+    elif histtype == "band":
+        band_defaults = {
+            "alpha": 0.5,
+            "edgecolor": "lightgray",
+            "hatch": "///",
+        }
+        for i in range(len(plottables)):
+            _kwargs = _chunked_kwargs[i]
+            _f = ax.stairs(
+                **plottables[i].to_stairband(),
+                label=_labels[i],
+                fill=True,
+                **soft_update_kwargs(_kwargs, band_defaults),
+            )
+            return_artists.append(StairsArtists(_f, None, None))
+        _artist = _f
+
     elif histtype == "errorbar":
         err_defaults = {
             "linestyle": "none",
@@ -480,14 +497,15 @@ def iterable_not_string(arg):
             _xerr = None
 
         for i in range(len(plottables)):
+            _kwargs = _chunked_kwargs[i]
             _plot_info = plottables[i].to_errorbar()
             if yerr is False:
                 _plot_info["yerr"] = None
             _plot_info["xerr"] = _xerr
             _e = ax.errorbar(
                 **_plot_info,
                 label=_labels[i],
-                **soft_update_kwargs(_chunked_kwargs[i], err_defaults),
+                **soft_update_kwargs(_kwargs, err_defaults),
             )
             return_artists.append(ErrorBarArtists(_e))
 

src/mplhep/utils.py

@@ -265,6 +265,14 @@ def density(self, boolean: bool):
     def to_stairs(self):
         return {"values": self.values, "edges": self.edges, "baseline": self.baseline}
 
+    def to_stairband(self):
+        self.errors()
+        return {
+            "values": self.values + self.yerr_hi,
+            "edges": self.edges,
+            "baseline": self.values - self.yerr_lo,
+        }
+
     def to_errorbar(self):
         self.errors()
         return {