Uninformative error when creating Chord diagram

[gmontamat]

I was trying to create a Chord diagram based on https://github.com/ioam/holoviews/blob/master/examples/gallery/demos/bokeh/route_chord.ipynb
I assumed it should work on my dataframes since they were very similar to the ones in the examples. I got the error:

ValueError: None of the available storage backends were able to support the supplied data format.

The actual issue was that I had loop edges (connecting nodes to themselves) which doesn't happen on the sample airport routes dataset. Removing those loops fixed the issue but a more clear error message would have saved me a couple hours.

[philippjfr]

Thanks for filing this issue, that would indeed be helpful. It's not quite clear to me why loop edges shouldn't be supported so this might in fact be a bug but for now I've labeled the issue as an enhancement request.

[philippjfr]

Would you happen to have a small example to reproduce this?

[philippjfr]

Nevermind, this is sufficient:

hv.Chord([('A', 'B', 2), ('B', 'A', 3), ('A', 'A', 2)])

[gmontamat]

Is it possible to support loop edges in these charts? It would be nice to have them like on this plotly example.

[philippjfr]

@gmontamat It will be once the PR above is merged.

[gmontamat]

@philippjfr great news! Thanks.

[garfield2020]

What data structure is needed for holoview chord diagrams?
I am trying to feed the center_path dataframe

with
hv.Chord(center_path)
and it gives me the error:
Number of samples, -1, must be non-negative.

[philippjfr]

@garfield2020 Could you provide a full traceback, and preferably a reproducible example?

[garfield2020]

Heres the full traceback, thanks philipp!

[philippjfr]

Are there any negative values in your value column?

[garfield2020]

That worked! I filtered out the negative values, and no more error.
But now I run the code and still don't get a chord chart output:

[jbednar]

You should call hv.extension('bokeh') if you want graphical representations.

[garfield2020]

Perfect! thank you both

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