Plotting ExtensionArrays

[andrewgsavage]

I'd like to plot data from an ExtensionArray. This currently results in an error TypeError: Empty 'DataFrame': no numeric data to plot

This is because the EA data is filtered out. Adding the ExtensionDtype to the filter criteria makes the plot work.
https://github.com/pandas-dev/pandas/blob/master/pandas/plotting/_core.py#L367

numeric_data = data.select_dtypes(include=[np.number,
                                               "datetime",
                                               "datetimetz",
                                               "timedelta", 
                                               pint.PintType])

Could we get a property of the ExtensionDtype that flags the dtype as holding plotable numeric data?

[andrewgsavage]

related issue hgrecco/pint-pandas#9

[TomAugspurger]

What version of pandas?

#25590 coerces EAs to ndarray before plotting. If np.asarray(your_array) returns a numeric type then it should be passed through to matplotlib, though it'll be a regular NumPy dtype, not your extension dtype. Does that suffice?

[andrewgsavage]

'0.25.0.dev0+430.gc79b7bb' - from a few days ago with that merge included.

np.asarray(your_array) return an object dtype, so is filtered out by select_dtypes, eg:
np.array(df.length)
array([<Quantity(1, 'meter')>, <Quantity(2, 'meter')>], dtype=object)

so no it doesn't suffice.

Passing quantity objects as opposed to floats to matploblib will allow the units converting part of matplotlib to work.*

*with some changes to pint. Alternatively the ExtensionArray could provide a function to return something plotable, so we can provide <Quantity(array([0, 1]), 'meter')> to matplotlib

[andrewgsavage]

@TomAugspurger have you had a chance to look at this?

[TomAugspurger]

Most likely DataFrame.select_dtypes(include=[np.number]) should include extension array types whose .dtype._is_numeric is True.

…

On Wed, Jun 19, 2019 at 4:50 PM andrewgsavage ***@***.***> wrote: @TomAugspurger <https://github.com/TomAugspurger> have you had a chance to look at this? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#26173?email_source=notifications&email_token=AAKAOITNEHUOB2NUZKUJGGDP3KS3BA5CNFSM4HHLHBX2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODYDMJEI#issuecomment-503760017>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAKAOISS3LSIAS6YU2U2HL3P3KS3BANCNFSM4HHLHBXQ> .

[andrewgsavage]

fixed by #38246