WIP: 1d+2d coord plotting (#1737)

* If one coord for contour plot is 2d, broadcast!

* Some kind of test...

doc/whats-new.rst

@@ -21,6 +21,10 @@ v0.10.1 (unreleased)
 Enhancements
 ~~~~~~~~~~~~
 
+- :py:func:`~plot.contourf()` learned to contour 2D variables that have both a 1D co-ordinate (e.g. time) and a 2D co-ordinate (e.g. depth as a function of time).
+  By `Deepak Cherian <https://github.com/dcherian>`_.
+
+
 Bug fixes
 ~~~~~~~~~
 

xarray/plot/plot.py

@@ -453,6 +453,13 @@ def newplotfunc(darray, x=None, y=None, figsize=None, size=None,
         yval = darray[ylab].values
         zval = darray.to_masked_array(copy=False)
 
+        # check if we need to broadcast one dimension
+        if xval.ndim < yval.ndim:
+            xval = np.broadcast_to(xval, yval.shape)
+
+        if yval.ndim < xval.ndim:
+            yval = np.broadcast_to(yval, xval.shape)
+
         # May need to transpose for correct x, y labels
         # xlab may be the name of a coord, we have to check for dim names
         if darray[xlab].dims[-1] == darray.dims[0]:

xarray/tests/test_plot.py

@@ -107,6 +107,15 @@ def test2d_nonuniform_calls_contourf(self):
         a.coords['dim_1'] = [2, 1, 89]
         self.assertTrue(self.contourf_called(a.plot.contourf))
 
+    def test2d_1d_2d_coordinates_contourf(self):
+        sz = (20, 10)
+        depth = easy_array(sz)
+        a = DataArray(easy_array(sz), dims=['z', 'time'],
+                      coords={'depth': (['z', 'time'], depth),
+                              'time': np.linspace(0, 1, sz[1])})
+
+        a.plot.contourf(x='time', y='depth')
+
     def test3d(self):
         self.darray.plot()