ENH/VIZ: Allowing s parameter of scatter plots to be a column name

doc/source/whatsnew/v1.1.0.rst

@@ -452,6 +452,7 @@ Other
 - Fixed bug in :func:`pandas.testing.assert_series_equal` where dtypes were checked for ``Interval`` and ``ExtensionArray`` operands when ``check_dtype`` was ``False`` (:issue:`32747`)
 - Bug in :meth:`Series.map` not raising on invalid ``na_action`` (:issue:`32815`)
 - Bug in :meth:`DataFrame.__dir__` caused a segfault when using unicode surrogates in a column name (:issue:`25509`)
+- Bug in :meth:`DataFrame.plot.scatter` caused an error when plotting variable marker sizes (:issue:`32904`)
 
 .. ---------------------------------------------------------------------------
 

pandas/plotting/_core.py

@@ -1468,15 +1468,19 @@ def scatter(self, x, y, s=None, c=None, **kwargs):
         y : int or str
             The column name or column position to be used as vertical
             coordinates for each point.
-        s : scalar or array_like, optional
+        s : str, scalar or array_like, optional
             The size of each point. Possible values are:
 
+            - A string with the name of the column to be used for marker's size.
+
             - A single scalar so all points have the same size.
 
             - A sequence of scalars, which will be used for each point's size
               recursively. For instance, when passing [2,14] all points size
               will be either 2 or 14, alternatively.
 
+              .. versionchanged:: 1.1.0
+
         c : str, int or array_like, optional
             The color of each point. Possible values are:
 

pandas/plotting/_matplotlib/core.py

@@ -934,6 +934,8 @@ def __init__(self, data, x, y, s=None, c=None, **kwargs):
             # hide the matplotlib default for size, in case we want to change
             # the handling of this argument later
             s = 20
+        elif is_hashable(s) and s in data.columns:
+            s = data[s]
         super().__init__(data, x, y, s=s, **kwargs)
         if is_integer(c) and not self.data.columns.holds_integer():
             c = self.data.columns[c]

pandas/tests/plotting/test_frame.py

@@ -1306,6 +1306,13 @@ def test_plot_scatter_with_c(self):
         float_array = np.array([0.0, 1.0])
         df.plot.scatter(x="A", y="B", c=float_array, cmap="spring")
 
+    def test_plot_scatter_with_s(self):
+        # this refers to GH 32904
+        df = DataFrame(np.random.random((10, 3)) * 100, columns=["a", "b", "c"],)
+
+        ax = df.plot.scatter(x="a", y="b", s="c")
+        tm.assert_numpy_array_equal(df["c"].values, right=ax.collections[0].get_sizes())
+
     def test_scatter_colors(self):
         df = DataFrame({"a": [1, 2, 3], "b": [1, 2, 3], "c": [1, 2, 3]})
         with pytest.raises(TypeError):