Plot not returning when specify x/y in axis_arguments for chunked NetCDF

[epifanio]

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ALL software version info

• xarray

'2023.12.0'

• holoviews

'1.18.1'

Description of expected behavior and the observed behavior

When setting the x or y values in the arguments for hvplot.line the code hangs and never return

Complete, minimal, self-contained example code that reproduces the issue

import xarray as xr
import holoviews as hv
import hvplot.xarray

hv.renderer('bokeh').webgl = False 

test_url = "https://thredds.met.no/thredds/dodsC/met.no/observations/stations/SN99880.nc"
ds = xr.open_dataset(test_url)
var = 'air_temperature_2m'

# the following works:
axis_arguments = {'grid':True, 'title': 'title', 'widget_location': 'bottom', 'responsive': False}
ds[var].hvplot.line(**axis_arguments)

#  When trying to set  `x` or `y` values in the `**axis_arguments` for `hvplot.line` the code hangs and never return

axis_arguments = {'y': ds[var], 'grid':True, 'title': 'title', 'widget_location': 'bottom', 'responsive': False}
ds[var].hvplot.line(**axis_arguments)

# same for:

axis_arguments = {'x': ds[var], 'grid':True, 'title': 'title', 'widget_location': 'bottom', 'responsive': False}
ds[var].hvplot.line(**axis_arguments)

Stack traceback and/or browser JavaScript console output

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[24], line 1
----> 1 ds[var].hvplot.line(**axis_arguments)

File /opt/conda/lib/python3.11/site-packages/hvplot/plotting/core.py:370, in hvPlotTabular.line(self, x, y, **kwds)
    275 def line(self, x=None, y=None, **kwds):
    276     """
    277     The `line` plot connects the points with a continuous curve.
    278 
   (...)
    368     - Wiki: https://en.wikipedia.org/wiki/Line_chart
    369     """
--> 370     return self(x, y, kind="line", **kwds)

File /opt/conda/lib/python3.11/site-packages/hvplot/plotting/core.py:93, in hvPlotBase.__call__(self, x, y, kind, **kwds)
     91         return pn.panel(callback)
     92     if panel_dict:
---> 93         plot = self._get_converter(x, y, kind, **kwds)(kind, x, y)
     94         return pn.panel(plot, **panel_dict)
     96 return self._get_converter(x, y, kind, **kwds)(kind, x, y)

File /opt/conda/lib/python3.11/site-packages/hvplot/plotting/core.py:103, in hvPlotBase._get_converter(self, x, y, kind, **kwds)
    101 y = y or params.pop("y", None)
    102 kind = kind or params.pop("kind", None)
--> 103 return HoloViewsConverter(self._data, x, y, kind=kind, **params)

File /opt/conda/lib/python3.11/site-packages/hvplot/converter.py:405, in HoloViewsConverter.__init__(self, data, x, y, kind, by, use_index, group_label, value_label, backlog, persist, use_dask, crs, fields, groupby, dynamic, grid, legend, rot, title, xlim, ylim, clim, symmetric, logx, logy, loglog, hover, subplots, label, invert, stacked, colorbar, datashade, rasterize, downsample, resample_when, row, col, debug, framewise, aggregator, projection, global_extent, geo, precompute, flip_xaxis, flip_yaxis, dynspread, hover_cols, x_sampling, y_sampling, project, tools, attr_labels, coastline, tiles, sort_date, check_symmetric_max, transforms, stream, cnorm, features, rescale_discrete_levels, autorange, **kwds)
    403 self.value_label = value_label
    404 self.label = label
--> 405 self._process_data(
    406     kind, data, x, y, by, groupby, row, col, use_dask,
    407     persist, backlog, label, group_label, value_label,
    408     hover_cols, attr_labels, transforms, stream, kwds
    409 )
    411 self.dynamic = dynamic
    412 self.geo = any([geo, crs, global_extent, projection, project, coastline, features])

File /opt/conda/lib/python3.11/site-packages/hvplot/converter.py:819, in HoloViewsConverter._process_data(self, kind, data, x, y, by, groupby, row, col, use_dask, persist, backlog, label, group_label, value_label, hover_cols, attr_labels, transforms, stream, kwds)
    817     other_dims = []
    818 da = data
--> 819 data, x, y, by_new, groupby_new = process_xarray(
    820     data, x, y, by, groupby, use_dask, persist, gridded,
    821     label, value_label, other_dims, kind=kind)
    823 if kind not in self._stats_types:
    824     if by is None: by = by_new

File /opt/conda/lib/python3.11/site-packages/hvplot/util.py:480, in process_xarray(data, x, y, by, groupby, use_dask, persist, gridded, label, value_label, other_dims, kind)
    478 covered_dims = []
    479 for var in all_vars:
--> 480     if var in dataset.coords:
    481         covered_dims.extend(dataset[var].dims)
    482 leftover_dims = [dim for dim in index_dims
    483                  if dim not in covered_dims + all_vars]

File /opt/conda/lib/python3.11/site-packages/xarray/core/coordinates.py:104, in AbstractCoordinates.__contains__(self, key)
    103 def __contains__(self, key: Hashable) -> bool:
--> 104     return key in self._names

TypeError: unhashable type: 'DataArray'

[hoxbro]

As the error is happening in hvplot I will transfer it there.

[jsignell]

It looks like you are passing an xarray.DataArray object (ds[var]) as x and y when you should be passing a string (var, or 'air_temperature_2m'). I am wondering what you are trying to achieve though. The first plot which as you say works, looks like what I would be expecting to see:

Note that I added some filtering to get rid of some very large values in the data.

[epifanio]

The problem is some inconsistency in the method's behavior. The x: ds[var] syntax works fine for other datasets but not for this one, where the app will hang forever, blocking the service (bokeh/panel serve) to resolve further requests. So if the use of x: ds[var] is not supported, an exception should be raised.

That specific dataset has a fillnull value; which I get rid of with ds.where(ds!= 9.96921e36)