Plot2D no longer sorts coordinates before plotting

[fmaussion]

I have a dataset with decreasing latitude coordinates.

With xarray v0.10.8, this is what happens when plotting:

But on latest master the image is now upside down:

Sorry if I missed a change along the way, I was off for a long time.

[shoyer]

cc @dcherian

[shoyer]

The most likely source here is #2294

[fmaussion]

Looks like a difficult thing to test, also...

[dcherian]

Yes #2294 changed the default xincrease, yincrease to be None rather than True. Previously, if xincrease was True we were setting axis limits and this prevented the axis from auto-updating its limits. Now that we are using the invert_axis() method, this might not be an issue. (Actually, now that I look at the code for invert_axis(), all I needed to do earlier was set the kwarg auto=None in the call to set_xlim, so this would be an easy way to revert to the previous code.)

I switched the default to None because I thought it was better to make the least number of modifications to the axis by default.

That said, I cannot reproduce this with a dataset with decreasing latitude so I'm very confused about what's happening.

da = xr.DataArray(np.arange(24).reshape(3,8), dims=('latitude', 'longitude'),
                 coords={'latitude': [8, 0, -8],
                        'longitude': np.arange(8)})

da.plot()

PS: I'm on a ship in the middle of the Pacific with crappy internet access. @fmaussion I'd appreciate it if you could look at this so we can get the release out. I will respond but there'll be a large time lag.

[fmaussion]

I cannot reproduce this with a dataset with decreasing latitude

Maybe a MPL version issue? Because our docs are also afffected, see:

• http://xarray.pydata.org/en/stable/plotting.html#two-dimensions
• http://xarray.pydata.org/en/latest/plotting.html#two-dimensions

@fmaussion I'd appreciate it if you could look at this

I will have a look now

[shoyer]

I think this is fixed by #2425?