Handle array dim with size one in plt.imshow

xarray/plot/plot.py

@@ -580,8 +580,15 @@ def imshow(x, y, z, ax, **kwargs):
                          'pcolormesh or contour(f)')
 
     # Centering the pixels- Assumes uniform spacing
-    xstep = (x[1] - x[0]) / 2.0
-    ystep = (y[1] - y[0]) / 2.0
+    try:
+        xstep = (x[1] - x[0]) / 2.0
+    except IndexError:
+        # Arbitrary default value, similar to matplotlib behaviour
+        xstep = .1
+    try:
+        ystep = (y[1] - y[0]) / 2.0
+    except IndexError:
+        ystep = .1
     left, right = x[0] - xstep, x[-1] + xstep
     bottom, top = y[-1] + ystep, y[0] - ystep
 
@@ -634,6 +641,8 @@ def _infer_interval_breaks(coord, axis=0):
     """
     coord = np.asarray(coord)
     deltas = 0.5 * np.diff(coord, axis=axis)
+    if deltas.size == 0:
+        deltas = np.array(0.0)
     first = np.take(coord, [0], axis=axis) - np.take(deltas, [0], axis=axis)
     last = np.take(coord, [-1], axis=axis) + np.take(deltas, [-1], axis=axis)
     trim_last = tuple(slice(None, -1) if n == axis else slice(None)

xarray/tests/test_plot.py

@@ -628,6 +628,10 @@ def test_can_plot_all_nans(self):
         # regression test for issue #1780
         self.plotfunc(DataArray(np.full((2, 2), np.nan)))
 
+    def test_can_plot_axis_size_one(self):
+        if self.plotfunc.__name__ not in ('contour', 'contourf'):
+            self.plotfunc(DataArray(np.ones((1, 1))))
+
     def test_viridis_cmap(self):
         cmap_name = self.plotmethod(cmap='viridis').get_cmap().name
         self.assertEqual('viridis', cmap_name)