matplotlib · jklymak · May 12, 2019 · Mar 22, 2019 · Mar 22, 2019 · Mar 22, 2019
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -1565,8 +1565,8 @@ def have_units(self):
         return self.converter is not None or self.units is not None
 
     def convert_units(self, x):
-        # If x is already a number, doesn't need converting
-        if munits.ConversionInterface.is_numlike(x):
+        # If x is natively supported by Matplotlib, doesn't need converting
+        if munits.ConversionInterface.is_natively_supported(x):
             return x
 
         if self.converter is None:

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -11,6 +11,7 @@
 import numpy as np
 from numpy import ma
 from cycler import cycler
+from decimal import Decimal
 import pytest
 
 import warnings
@@ -1477,6 +1478,62 @@ def test_bar_tick_label_multiple_old_alignment():
            align='center')
 
 
+@check_figures_equal(extensions=["png"])
+def test_bar_decimal_center(fig_test, fig_ref):
+    ax = fig_test.subplots()
+    x0 = [1.5, 8.4, 5.3, 4.2]
+    y0 = [1.1, 2.2, 3.3, 4.4]
+    x = [Decimal(x) for x in x0]
+    y = [Decimal(y) for y in y0]
+    # Test image - vertical, align-center bar chart with Decimal() input
+    ax.bar(x, y, align='center')
+    # Reference image
+    ax = fig_ref.subplots()
+    ax.bar(x0, y0, align='center')
+
+
+@check_figures_equal(extensions=["png"])
+def test_barh_decimal_center(fig_test, fig_ref):
+    ax = fig_test.subplots()
+    x0 = [1.5, 8.4, 5.3, 4.2]
+    y0 = [1.1, 2.2, 3.3, 4.4]
+    x = [Decimal(x) for x in x0]
+    y = [Decimal(y) for y in y0]
+    # Test image - horizontal, align-center bar chart with Decimal() input
+    ax.barh(x, y, height=[0.5, 0.5, 1, 1], align='center')
+    # Reference image
+    ax = fig_ref.subplots()
+    ax.barh(x0, y0, height=[0.5, 0.5, 1, 1], align='center')
+
+
+@check_figures_equal(extensions=["png"])
+def test_bar_decimal_width(fig_test, fig_ref):
+    x = [1.5, 8.4, 5.3, 4.2]
+    y = [1.1, 2.2, 3.3, 4.4]
+    w0 = [0.7, 1.45, 1, 2]
+    w = [Decimal(i) for i in w0]
+    # Test image - vertical bar chart with Decimal() width
+    ax = fig_test.subplots()
+    ax.bar(x, y, width=w, align='center')
+    # Reference image
+    ax = fig_ref.subplots()
+    ax.bar(x, y, width=w0, align='center')
+
+
+@check_figures_equal(extensions=["png"])
+def test_barh_decimal_height(fig_test, fig_ref):
+    x = [1.5, 8.4, 5.3, 4.2]
+    y = [1.1, 2.2, 3.3, 4.4]
+    h0 = [0.7, 1.45, 1, 2]
+    h = [Decimal(i) for i in h0]
+    # Test image - horizontal bar chart with Decimal() height
+    ax = fig_test.subplots()
+    ax.barh(x, y, height=h, align='center')
+    # Reference image
+    ax = fig_ref.subplots()
+    ax.barh(x, y, height=h0, align='center')
+
+
 def test_bar_color_none_alpha():
     ax = plt.gca()
     rects = ax.bar([1, 2], [2, 4], alpha=0.3, color='none', edgecolor='r')
@@ -1819,6 +1876,21 @@ def test_scatter_2D(self):
         fig, ax = plt.subplots()
         ax.scatter(x, y, c=z, s=200, edgecolors='face')
 
+    @check_figures_equal(extensions=["png"])
+    def test_scatter_decimal(self, fig_test, fig_ref):
+        x0 = np.array([1.5, 8.4, 5.3, 4.2])
+        y0 = np.array([1.1, 2.2, 3.3, 4.4])
+        x = np.array([Decimal(i) for i in x0])
+        y = np.array([Decimal(i) for i in y0])
+        c = ['r', 'y', 'b', 'lime']
+        s = [24, 15, 19, 29]
+        # Test image - scatter plot with Decimal() input
+        ax = fig_test.subplots()
+        ax.scatter(x, y, c=c, s=s)
+        # Reference image
+        ax = fig_ref.subplots()
+        ax.scatter(x0, y0, c=c, s=s)
+
     def test_scatter_color(self):
         # Try to catch cases where 'c' kwarg should have been used.
         with pytest.raises(ValueError):
@@ -5965,6 +6037,18 @@ def test_plot_columns_cycle_deprecation():
         plt.plot(np.zeros((2, 2)), np.zeros((2, 3)))
 
 
+@check_figures_equal(extensions=["png"])
+def test_plot_decimal(fig_test, fig_ref):
+    x0 = np.arange(-10, 10, 0.3)
+    y0 = [5.2 * x ** 3 - 2.1 * x ** 2 + 7.34 * x + 4.5 for x in x0]
+    x = [Decimal(i) for i in x0]
+    y = [Decimal(i) for i in y0]
+    # Test image - line plot with Decimal input
+    fig_test.subplots().plot(x, y)
+    # Reference image
+    fig_ref.subplots().plot(x0, y0)
+
+
 # pdf and svg tests fail using travis' old versions of gs and inkscape.
 @check_figures_equal(extensions=["png"])
 def test_markerfacecolor_none_alpha(fig_test, fig_ref):

diff --git a/lib/matplotlib/units.py b/lib/matplotlib/units.py
@@ -45,6 +45,8 @@ def default_units(x, axis):
 from numbers import Number
 
 import numpy as np
+from numpy import ma
+from decimal import Decimal
 
 from matplotlib import cbook
 
@@ -132,6 +134,58 @@ def is_numlike(x):
         else:
             return isinstance(x, Number)
 
+    @staticmethod
+    def is_natively_supported(x):
+        """
+        Return whether *x* is of a type that Matplotlib natively supports or
+        *x* is array of objects of such types.
+        """
+        # Matplotlib natively supports all number types except Decimal
+        if np.iterable(x):
+            # Assume lists are homogeneous as other functions in unit system
+            for thisx in x:
+                return (isinstance(thisx, Number) and
+                        not isinstance(thisx, Decimal))
+        else:
+            return isinstance(x, Number) and not isinstance(x, Decimal)
+
+
+class DecimalConverter(ConversionInterface):
+    """
+    Converter for decimal.Decimal data to float.
+    """
+    @staticmethod
+    def convert(value, unit, axis):
+        """
+        Convert Decimals to floats.
+
+        The *unit* and *axis* arguments are not used.
+
+        Parameters
+        ----------
+        value : decimal.Decimal or iterable
+            Decimal or list of Decimal need to be converted
+        """
+        # If value is a Decimal
+        if isinstance(value, Decimal):
+            return np.float(value)
+        else:
+            # assume x is a list of Decimal
+            converter = np.asarray
+            if isinstance(value, ma.MaskedArray):
+                converter = ma.asarray
+            return converter(value, dtype=np.float)
+
+    @staticmethod
+    def axisinfo(unit, axis):
+        # Since Decimal is a kind of Number, don't need specific axisinfo.
+        return AxisInfo()
+
+    @staticmethod
+    def default_units(x, axis):
+        # Return None since Decimal is a kind of Number.
+        return None
+
 
 class Registry(dict):
     """Register types with conversion interface."""
@@ -164,3 +218,4 @@ def get_converter(self, x):
 
 
 registry = Registry()
+registry[Decimal] = DecimalConverter()