From 788abaf0339894c151afa188367dfd3ed26738e9 Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Thu, 21 Sep 2017 22:09:26 -0400
Subject: [PATCH] Backport PR #9168: Fix pcolormesh and DatetimeIndex error

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   PR Summary

Fixes issue with `DatetimeIndex` and `pcolormesh`: https://github.com/matplotlib/matplotlib/issues/9167

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   PR Checklist

- [X ] Code is PEP 8 compliant

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---
 lib/matplotlib/axes/_axes.py      |  5 +++--
 lib/matplotlib/tests/test_axes.py | 11 +++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index 402382587ccf..48126b6be55e 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -5620,7 +5620,8 @@ def pcolormesh(self, *args, **kwargs):
 
         X, Y, C = self._pcolorargs('pcolormesh', *args, allmatch=allmatch)
         Ny, Nx = X.shape
-
+        X = X.ravel()
+        Y = Y.ravel()
         # unit conversion allows e.g. datetime objects as axis values
         self._process_unit_info(xdata=X, ydata=Y, kwargs=kwargs)
         X = self.convert_xunits(X)
@@ -5628,7 +5629,7 @@ def pcolormesh(self, *args, **kwargs):
 
         # convert to one dimensional arrays
         C = C.ravel()
-        coords = np.column_stack((X.flat, Y.flat)).astype(float, copy=False)
+        coords = np.column_stack((X, Y)).astype(float, copy=False)
 
         collection = mcoll.QuadMesh(Nx - 1, Ny - 1, coords,
                                     antialiased=antialiased, shading=shading,
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index b96b525aa439..25a4fff43edc 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -4929,6 +4929,17 @@ def test_broken_barh_empty():
     ax.broken_barh([], (.1, .5))
 
 
+def test_pandas_pcolormesh():
+    pd = pytest.importorskip('pandas')
+
+    time = pd.date_range('2000-01-01', periods=10)
+    depth = np.arange(20)
+    data = np.random.rand(20, 10)
+
+    fig, ax = plt.subplots()
+    ax.pcolormesh(time, depth, data)
+
+
 def test_pandas_indexing_dates():
     pd = pytest.importorskip('pandas')