BUG/PLT: Multiple plots with different cmap, colorbars legends use first cmap (#33392)

Author: charlesdong1991

doc/source/whatsnew/v1.1.0.rst

@@ -523,6 +523,7 @@ Plotting
 - :func:`.plot` for line/bar now accepts color by dictonary (:issue:`8193`).
 - Bug in :meth:`DataFrame.plot.hist` where weights are not working for multiple columns (:issue:`33173`)
 - Bug in :meth:`DataFrame.boxplot` and :meth:`DataFrame.plot.boxplot` lost color attributes of ``medianprops``, ``whiskerprops``, ``capprops`` and ``medianprops`` (:issue:`30346`)
+- Bug in :meth:`DataFrame.plot.scatter` that when adding multiple plots with different ``cmap``, colorbars alway use the first ``cmap`` (:issue:`33389`)
 
 
 Groupby/resample/rolling

pandas/plotting/_matplotlib/core.py

@@ -902,7 +902,11 @@ def _plot_colorbar(self, ax, **kwds):
         # For a more detailed description of the issue
         # see the following link:
         # https://github.com/ipython/ipython/issues/11215
-        img = ax.collections[0]
+
+        # GH33389, if ax is used multiple times, we should always
+        # use the last one which contains the latest information
+        # about the ax
+        img = ax.collections[-1]
         cbar = self.fig.colorbar(img, ax=ax, **kwds)
 
         if _mpl_ge_3_0_0():

pandas/tests/plotting/test_frame.py

@@ -1332,6 +1332,20 @@ def test_scatter_colors(self):
             np.array([1, 1, 1, 1], dtype=np.float64),
         )
 
+    def test_scatter_colorbar_different_cmap(self):
+        # GH 33389
+        import matplotlib.pyplot as plt
+
+        df = pd.DataFrame({"x": [1, 2, 3], "y": [1, 3, 2], "c": [1, 2, 3]})
+        df["x2"] = df["x"] + 1
+
+        fig, ax = plt.subplots()
+        df.plot("x", "y", c="c", kind="scatter", cmap="cividis", ax=ax)
+        df.plot("x2", "y", c="c", kind="scatter", cmap="magma", ax=ax)
+
+        assert ax.collections[0].cmap.name == "cividis"
+        assert ax.collections[1].cmap.name == "magma"
+
     @pytest.mark.slow
     def test_plot_bar(self):
         df = DataFrame(