Fix RGB imshow with X or Y dim of size one (#1967)

Author: Zac-HD

doc/whats-new.rst

@@ -64,6 +64,9 @@ Bug fixes
   By `Keisuke Fujii <https://github.com/fujiisoup>`_.
 - Fix kwarg `colors` clashing with auto-inferred `cmap` (:issue:`1461`)
   By `Deepak Cherian <https://github.com/dcherian>`_.
+- Fix :py:func:`~xarray.plot.imshow` error when passed an RGB array with
+  size one in a spatial dimension.
+  By `Zac Hatfield-Dodds <https://github.com/Zac-HD>`_.
 
 .. _whats-new.0.10.1:
 

xarray/plot/utils.py

@@ -296,7 +296,7 @@ def _infer_xy_labels_3d(darray, x, y, rgb):
     assert rgb is not None
 
     # Finally, we pick out the red slice and delegate to the 2D version:
-    return _infer_xy_labels(darray.isel(**{rgb: 0}).squeeze(), x, y)
+    return _infer_xy_labels(darray.isel(**{rgb: 0}), x, y)
 
 
 def _infer_xy_labels(darray, x, y, imshow=False, rgb=None):

xarray/tests/test_plot.py

@@ -1197,6 +1197,11 @@ def test_imshow_rgb_values_in_valid_range(self):
         assert out.dtype == np.uint8
         assert (out[..., :3] == da.values).all()  # Compare without added alpha
 
+    def test_regression_rgb_imshow_dim_size_one(self):
+        # Regression: https://github.com/pydata/xarray/issues/1966
+        da = DataArray(easy_array((1, 3, 3), start=0.0, stop=1.0))
+        da.plot.imshow()
+
 
 class TestFacetGrid(PlotTestCase):
     def setUp(self):