Don't use offset / scientific notation in numeric legends (#3187)

* Don't show offset / scientific notation in numeric legends

* Update release notes

Author: mwaskom

doc/whatsnew/v0.12.2.rst

@@ -6,6 +6,8 @@ v0.12.2 (Unreleased)
 
 - |Enhancement| Automatic mark widths are now calculated separately for unshared facet axes (:pr:`3119`).
 
+- |Fix| Fixed a bug where legends for numeric variables with large values with be incorrectly shown (i.e. with a missing offset or exponent; :pr:`3187`).
+
 - |Fix| Fixed a regression in v0.12.0 where manually-added labels could have duplicate legend entries (:pr:`3116`).
 
 - |Fix| Fixed a bug in :func:`histplot` with `kde=True` and `log_scale=True` where the curve was not scaled properly (:pr:`3173`).

seaborn/_core/scales.py

@@ -378,6 +378,14 @@ def spacer(x):
             axis.set_view_interval(vmin, vmax)
             locs = axis.major.locator()
             locs = locs[(vmin <= locs) & (locs <= vmax)]
+            # Avoid having an offset / scientific notation in a legend
+            # as we don't represent that anywhere so it ends up incorrect.
+            # This could become an option (e.g. Continuous.label(offset=True))
+            # in which case we would need to figure out how to show it.
+            if hasattr(axis.major.formatter, "set_useOffset"):
+                axis.major.formatter.set_useOffset(False)
+            if hasattr(axis.major.formatter, "set_scientific"):
+                axis.major.formatter.set_scientific(False)
             labels = axis.major.formatter.format_ticks(locs)
             new._legend = list(locs), list(labels)
 

seaborn/utils.py

@@ -699,6 +699,10 @@ def get_view_interval(self):
         formatter = mpl.ticker.LogFormatter()
     else:
         formatter = mpl.ticker.ScalarFormatter()
+        # Avoid having an offset/scientific notation which we don't currently
+        # have any way of representing in the legend
+        formatter.set_useOffset(False)
+        formatter.set_scientific(False)
     formatter.axis = dummy_axis()
 
     # TODO: The following two lines should be replaced

tests/_core/test_plot.py

@@ -2051,6 +2051,15 @@ def _legend_artist(self, variables, value, scales):
         p = Plot(**xy, color=["a", "b", "c", "d"]).add(NoLegendMark()).plot()
         assert not p._figure.legends
 
+    def test_legend_has_no_offset(self, xy):
+
+        color = np.add(xy["x"], 1e8)
+        p = Plot(**xy, color=color).add(MockMark()).plot()
+        legend = p._figure.legends[0]
+        assert legend.texts
+        for text in legend.texts:
+            assert float(text.get_text()) > 1e7
+
 
 class TestDefaultObject:
 

tests/test_relational.py

@@ -675,6 +675,12 @@ def test_ax_kwarg_removal(self, long_df):
         assert len(ax.collections) == 0
         assert len(g.ax.collections) > 0
 
+    def test_legend_has_no_offset(self, long_df):
+
+        g = relplot(data=long_df, x="x", y="y", hue=long_df["z"] + 1e8)
+        for text in g.legend.texts:
+            assert float(text.get_text()) > 1e7
+
 
 class TestLinePlotter(SharedAxesLevelTests, Helpers):