Squashed commit of the following:

commit 37a947a
Author: Deepak Cherian <[email protected]>
Date:   Wed Jan 30 09:20:57 2019 -0800

    Refactor plot utils (#2670)

    * Refactor out utility functions.

    * facetgrid refactor

    1. refactor out _easy_facetgrid
    2. Combine map_dataarray_line with map_dataarray

    * flake8

    * Refactor out colorbar making to plot.utils._add_colorbar

    * Refactor out cmap_params, cbar_kwargs processing

    * Back to map_dataarray_line

    * lint

    * small rename

    * review comment.

    * Move _infer_line_data back.

commit fd2552a
Author: Spencer Clark <[email protected]>
Date:   Wed Jan 30 11:45:09 2019 -0500

    Enable subtracting a scalar cftime.datetime object from a CFTimeIndex (#2672)

    * Enable subtracting a scalar cftime.datetime object from a CFTimeIndex

    * lint

    * Test cftime.datetime minus CFTimeIndex as well

    * Fix cftime minus CFTimeIndex

commit e8bf4bf
Author: Tom Nicholas <[email protected]>
Date:   Wed Jan 30 02:02:22 2019 +0000

    Bugfix for line plot axes (#2726)

    * Fixed logic for setting line data

    * Added tests to check line data matches values of correct coords

    * Recorded bugfix for line plots

    * Update doc/whats-new.rst

    Co-Authored-By: TomNicholas <[email protected]>

    * Update doc/whats-new.rst

    Co-Authored-By: TomNicholas <[email protected]>

commit 620b946
Author: Stephan Hoyer <[email protected]>
Date:   Sun Jan 27 13:02:03 2019 -0800

    Fix test failures / warnings for pandas 0.24 (#2720)

    * Fix test failures / warnings for pandas 0.24

    Fixes GH2717

    * Brief doc note

    * Comment on name order

commit 882deac
Author: Stephan Hoyer <[email protected]>
Date:   Sun Jan 27 09:11:47 2019 -0800

    DOC: refresh whats-new for 0.11.3 / 0.12.0 (#2718)

commit 8ca8efe
Author: Stephan Hoyer <[email protected]>
Date:   Sat Jan 26 10:14:49 2019 -0800

    Update environment for doc build (#2708)

    * Update environment for doc build

    We were pinning very old versions for most of these packages. This should
    fix the failures on ReadTheDocs.

    * Build fixes

commit 2e99c7d
Author: Stephan Hoyer <[email protected]>
Date:   Fri Jan 25 13:52:17 2019 -0800

    Print full environment fron conf.py (#2709)

    This should make it easier to debug the doc build environment.

commit cc5015a
Author: Stephan Hoyer <[email protected]>
Date:   Fri Jan 25 11:55:07 2019 -0800

    BUG: ensure indexes are reset when coords are modified (#2707)

    This was introduced by the recent indexes refactor, but never made it into a
    release.

commit aabda43
Author: Joe Hamman <[email protected]>
Date:   Fri Jan 25 08:38:45 2019 -0800

    Remove py2 compat (#2645)

    * strip out PY2 compat code from pycompat.py

    * isort

    * remove 2 unused imports

    * remove extra import

    * no more future

    * no unicode literals

    * no more ReprMixin

    * cleanup merge

    * remove deprecated imports from collections

    * 2 more cleanups from shoyer

Author: dcherian

doc/whats-new.rst

@@ -58,6 +58,12 @@ Bug fixes
   from higher frequencies to lower frequencies.  Datapoints outside the bounds
   of the original time coordinate are now filled with NaN (:issue:`2197`). By
   `Spencer Clark <https://github.com/spencerkclark>`_.
+- Line plots with the `x` argument set to a non-dimensional coord now plot the correct data for 1D DataArrays.
+  (:issue:`27251). By `Tom Nicholas <http://github.com/TomNicholas>`_.
+- Subtracting a scalar ``cftime.datetime`` object from a
+  :py:class:`CFTimeIndex` now results in a :py:class:`pandas.TimedeltaIndex`
+  instead of raising a ``TypeError`` (:issue:`2671`).  By `Spencer Clark
+  <https://github.com/spencerkclark>`_.
 
 .. _whats-new.0.11.3:
 

xarray/coding/cftimeindex.py

@@ -408,13 +408,17 @@ def __radd__(self, other):
         return CFTimeIndex(other + np.array(self))
 
     def __sub__(self, other):
-        if isinstance(other, CFTimeIndex):
+        import cftime
+        if isinstance(other, (CFTimeIndex, cftime.datetime)):
             return pd.TimedeltaIndex(np.array(self) - np.array(other))
         elif isinstance(other, pd.TimedeltaIndex):
             return CFTimeIndex(np.array(self) - other.to_pytimedelta())
         else:
             return CFTimeIndex(np.array(self) - other)
 
+    def __rsub__(self, other):
+        return pd.TimedeltaIndex(other - np.array(self))
+
     def _add_delta(self, deltas):
         # To support TimedeltaIndex + CFTimeIndex with older versions of
         # pandas.  No longer used as of pandas 0.23.

xarray/core/missing.py

@@ -10,7 +10,7 @@
 from .common import _contains_datetime_like_objects
 from .computation import apply_ufunc
 from .duck_array_ops import dask_array_type
-from .utils import OrderedSet, is_scalar
+from .utils import OrderedSet, datetime_to_numeric, is_scalar
 from .variable import Variable, broadcast_variables
 
 

xarray/plot/facetgrid.py

@@ -7,7 +7,7 @@
 
 from ..core.formatting import format_item
 from .utils import (
-    _infer_line_data, _infer_xy_labels, _process_cmap_cbar_kwargs,
+    _infer_xy_labels, _process_cmap_cbar_kwargs,
     import_matplotlib_pyplot, label_from_attrs)
 
 # Overrides axes.labelsize, xtick.major.size, ytick.major.size
@@ -224,6 +224,7 @@ def map_dataarray(self, func, x, y, **kwargs):
 
         cmap_params, cbar_kwargs = _process_cmap_cbar_kwargs(
             func, kwargs, self.data.values)
+
         self._cmap_extend = cmap_params.get('extend')
 
         # Order is important
@@ -251,6 +252,7 @@ def map_dataarray(self, func, x, y, **kwargs):
         return self
 
     def map_dataarray_line(self, func, x, y, **kwargs):
+        from .plot import _infer_line_data
 
         add_legend = kwargs.pop('add_legend', True)
         kwargs['add_legend'] = False

xarray/plot/plot.py

@@ -15,13 +15,100 @@
 
 from .facetgrid import _easy_facetgrid
 from .utils import (
+<<<<<<< HEAD
     _add_colorbar, _ensure_plottable, _infer_interval_breaks, _infer_line_data,
     _infer_xy_labels, _interval_to_double_bound_points,
     _interval_to_mid_points, _process_cmap_cbar_kwargs, _rescale_imshow_rgb,
     _resolve_intervals_2dplot, _update_axes, _valid_other_type, get_axis,
     import_matplotlib_pyplot, label_from_attrs)
 
 
+=======
+    _add_colorbar, _ensure_plottable, _infer_interval_breaks, _infer_xy_labels,
+    _interval_to_double_bound_points, _interval_to_mid_points,
+    _process_cmap_cbar_kwargs, _rescale_imshow_rgb, _resolve_intervals_2dplot,
+    _update_axes, _valid_other_type, get_axis, import_matplotlib_pyplot,
+    label_from_attrs)
+
+
+def _infer_line_data(darray, x, y, hue):
+    error_msg = ('must be either None or one of ({0:s})'
+                 .format(', '.join([repr(dd) for dd in darray.dims])))
+    ndims = len(darray.dims)
+
+    if x is not None and x not in darray.dims and x not in darray.coords:
+        raise ValueError('x ' + error_msg)
+
+    if y is not None and y not in darray.dims and y not in darray.coords:
+        raise ValueError('y ' + error_msg)
+
+    if x is not None and y is not None:
+        raise ValueError('You cannot specify both x and y kwargs'
+                         'for line plots.')
+
+    if ndims == 1:
+        huename = None
+        hueplt = None
+        huelabel = ''
+
+        if x is not None:
+            xplt = darray[x]
+            yplt = darray
+
+        elif y is not None:
+            xplt = darray
+            yplt = darray[y]
+
+        else:  # Both x & y are None
+            dim = darray.dims[0]
+            xplt = darray[dim]
+            yplt = darray
+
+    else:
+        if x is None and y is None and hue is None:
+            raise ValueError('For 2D inputs, please'
+                             'specify either hue, x or y.')
+
+        if y is None:
+            xname, huename = _infer_xy_labels(darray=darray, x=x, y=hue)
+            xplt = darray[xname]
+            if xplt.ndim > 1:
+                if huename in darray.dims:
+                    otherindex = 1 if darray.dims.index(huename) == 0 else 0
+                    otherdim = darray.dims[otherindex]
+                    yplt = darray.transpose(otherdim, huename)
+                    xplt = xplt.transpose(otherdim, huename)
+                else:
+                    raise ValueError('For 2D inputs, hue must be a dimension'
+                                     + ' i.e. one of ' + repr(darray.dims))
+
+            else:
+                yplt = darray.transpose(xname, huename)
+
+        else:
+            yname, huename = _infer_xy_labels(darray=darray, x=y, y=hue)
+            yplt = darray[yname]
+            if yplt.ndim > 1:
+                if huename in darray.dims:
+                    otherindex = 1 if darray.dims.index(huename) == 0 else 0
+                    xplt = darray.transpose(otherdim, huename)
+                else:
+                    raise ValueError('For 2D inputs, hue must be a dimension'
+                                     + ' i.e. one of ' + repr(darray.dims))
+
+            else:
+                xplt = darray.transpose(yname, huename)
+
+        huelabel = label_from_attrs(darray[huename])
+        hueplt = darray[huename]
+
+    xlabel = label_from_attrs(xplt)
+    ylabel = label_from_attrs(yplt)
+
+    return xplt, yplt, hueplt, xlabel, ylabel, huelabel
+
+
+>>>>>>> upstream/master
 def plot(darray, row=None, col=None, col_wrap=None, ax=None, hue=None,
          rtol=0.01, subplot_kws=None, **kwargs):
     """
@@ -603,6 +690,10 @@ def newplotfunc(darray, x=None, y=None, figsize=None, size=None,
                 cbar_kwargs['label'] = label_from_attrs(darray)
             cbar = _add_colorbar(primitive, ax, cbar_ax, cbar_kwargs,
                                  cmap_params)
+<<<<<<< HEAD
+=======
+
+>>>>>>> upstream/master
         elif (cbar_ax is not None or cbar_kwargs):
             # inform the user about keywords which aren't used
             raise ValueError("cbar_ax and cbar_kwargs can't be used with "

xarray/plot/utils.py

@@ -6,6 +6,8 @@
 import numpy as np
 import pandas as pd
 
+from inspect import getfullargspec
+
 from ..core.options import OPTIONS
 from ..core.utils import is_scalar
 

xarray/tests/test_cftimeindex.py

@@ -700,6 +700,26 @@ def test_cftimeindex_sub_cftimeindex(calendar):
     assert isinstance(result, pd.TimedeltaIndex)
 
 
+@pytest.mark.skipif(not has_cftime, reason='cftime not installed')
+@pytest.mark.parametrize('calendar', _CFTIME_CALENDARS)
+def test_cftimeindex_sub_cftime_datetime(calendar):
+    a = xr.cftime_range('2000', periods=5, calendar=calendar)
+    result = a - a[0]
+    expected = pd.TimedeltaIndex([timedelta(days=i) for i in range(5)])
+    assert result.equals(expected)
+    assert isinstance(result, pd.TimedeltaIndex)
+
+
+@pytest.mark.skipif(not has_cftime, reason='cftime not installed')
+@pytest.mark.parametrize('calendar', _CFTIME_CALENDARS)
+def test_cftime_datetime_sub_cftimeindex(calendar):
+    a = xr.cftime_range('2000', periods=5, calendar=calendar)
+    result = a[0] - a
+    expected = pd.TimedeltaIndex([timedelta(days=-i) for i in range(5)])
+    assert result.equals(expected)
+    assert isinstance(result, pd.TimedeltaIndex)
+
+
 @pytest.mark.skipif(not has_cftime, reason='cftime not installed')
 @pytest.mark.parametrize('calendar', _CFTIME_CALENDARS)
 def test_cftimeindex_sub_timedeltaindex(calendar):

xarray/tests/test_plot.py

@@ -4,6 +4,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+from numpy.testing import assert_array_equal
 
 import xarray as xr
 import xarray.plot as xplt
@@ -140,6 +141,20 @@ def test_1d_x_y_kw(self):
         with raises_regex(ValueError, 'None'):
             da.plot(x='z', y='f')
 
+    # Test for bug in GH issue #2725
+    def test_infer_line_data(self):
+        current = DataArray(name='I', data=np.array([5, 8]), dims=['t'],
+                            coords={'t': (['t'], np.array([0.1, 0.2])),
+                                    'V': (['t'], np.array([100, 200]))})
+
+        # Plot current against voltage
+        line = current.plot.line(x='V')[0]
+        assert_array_equal(line.get_xdata(), current.coords['V'].values)
+
+        # Plot current against time
+        line = current.plot.line()[0]
+        assert_array_equal(line.get_xdata(), current.coords['t'].values)
+
     def test_2d_line(self):
         with raises_regex(ValueError, 'hue'):
             self.darray[:, :, 0].plot.line()