Discourage use of plot_date()

timhoffm · timhoffm · commit bcae8a7763a1 · 2021-04-26T22:28:49.000+02:00
diff --git a/doc/api/next_api_changes/deprecations/18346-TH.rst b/doc/api/next_api_changes/deprecations/18346-TH.rst
@@ -0,0 +1,9 @@
+``plot_date``
+~~~~~~~~~~~~~
+The use of `~.Axes.plot_date` is discouraged. This method exists for historic
+reasons and may be deprecated in the future.
+
+- ``datetime``-like data should directly be plotted using `~.Axes.plot`.
+- If you need to plot plain numeric data as :ref:`date-format` or
+  need to set a timezone, call ``ax.xaxis.axis_date`` / ``ax.yaxis.axis_date``
+  before `~.Axes.plot`. See `.Axis.axis_date`.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -1616,7 +1616,7 @@ def plot_date(self, x, y, fmt='o', tz=None, xdate=True, ydate=False,
         """
         Plot co-ercing the axis to treat floats as dates.
 
-        .. note::
+        .. admonition:: Discouraged
 
             This method exists for historic reasons and will be deprecated in
             the future.
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -670,7 +670,8 @@ def test_single_date():
     data1 = [-65.54]
 
     fig, ax = plt.subplots(2, 1)
-    ax[0].plot_date(time1 + dt, data1, 'o', color='r')
+    with pytest.warns(PendingDeprecationWarning):
+        ax[0].plot_date(time1 + dt, data1, 'o', color='r')
     ax[1].plot(time1, data1, 'o', color='r')
 
 
@@ -5830,11 +5831,13 @@ def test_date_timezone_x():
     # Same Timezone
     plt.figure(figsize=(20, 12))
     plt.subplot(2, 1, 1)
-    plt.plot_date(time_index, [3] * 3, tz='Canada/Eastern')
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date(time_index, [3] * 3, tz='Canada/Eastern')
 
     # Different Timezone
     plt.subplot(2, 1, 2)
-    plt.plot_date(time_index, [3] * 3, tz='UTC')
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date(time_index, [3] * 3, tz='UTC')
 
 
 @image_comparison(['date_timezone_y.png'])
@@ -5847,12 +5850,14 @@ def test_date_timezone_y():
     # Same Timezone
     plt.figure(figsize=(20, 12))
     plt.subplot(2, 1, 1)
-    plt.plot_date([3] * 3,
-                  time_index, tz='Canada/Eastern', xdate=False, ydate=True)
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date([3] * 3,
+                      time_index, tz='Canada/Eastern', xdate=False, ydate=True)
 
     # Different Timezone
     plt.subplot(2, 1, 2)
-    plt.plot_date([3] * 3, time_index, tz='UTC', xdate=False, ydate=True)
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date([3] * 3, time_index, tz='UTC', xdate=False, ydate=True)
 
 
 @image_comparison(['date_timezone_x_and_y.png'], tol=1.0)
@@ -5865,11 +5870,13 @@ def test_date_timezone_x_and_y():
     # Same Timezone
     plt.figure(figsize=(20, 12))
     plt.subplot(2, 1, 1)
-    plt.plot_date(time_index, time_index, tz='UTC', ydate=True)
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date(time_index, time_index, tz='UTC', ydate=True)
 
     # Different Timezone
     plt.subplot(2, 1, 2)
-    plt.plot_date(time_index, time_index, tz='US/Eastern', ydate=True)
+    with pytest.warns(PendingDeprecationWarning):
+        plt.plot_date(time_index, time_index, tz='US/Eastern', ydate=True)
 
 
 @image_comparison(['axisbelow.png'], remove_text=True)
