ENH: plot_topomap, plot_joint & plot: API homogeneity for scalings/scale parameters

[kingjr]

Small API heterogenity: different plotting functions use similar parameters slightly differently (and named slightly differently)

• scaling: evoked.plot(scalings=dict()) but evoked.plot_topomap(scale=dict() | float)
• units: evoked.plot(units=dict()) but evoked.plot_topomap(unit=dict() | str)
• max amplitude: evoked.plot(ylim=dict()) but evoked.plot_topomap(vmin=dict() | float, vmax=dict() | float())

Changing parameter names can be annoying for deprecation, but I suggest we at least make their input similar (e.g. always accepts both dict and float).

Additionally, evoked.plot_joint() could gather the parameters common to plot() and plot_topomap() to simplify it. WDTY @jona-sassenhagen ?

[jona-sassenhagen]

Somewhat related: #3164

[jona-sassenhagen]

Unity here would be a great improved IMO.

We must be careful however with how different functions handle different channel types.

[jona-sassenhagen]

Can we split this into multiple smaller PRs?

[jaeilepp]

It feels a bit redundant to have scaling and vmin, vmax in the first place. Could we get rid of scaling in for instance topomaps or is there a use case where you'd prefer using scaling?

[agramfort]

to me scaling and vmin and vmax very different usage. I think we should keep them.

[jona-sassenhagen]

I think you need scaling if you use for example stats.regression, where you plot t values on data channels.

[jona-sassenhagen]

Ugh I must get back to this. @jaeilepp can you maybe assign me so I don't forget?

[jaeilepp]

Done.

[jona-sassenhagen]

Also: mne.viz.plot_compare_evokeds is missing a bunch of options, like scalings and units.

:(

[jona-sassenhagen]

@Eric89GXL @agramfort do you have any idea about solving the different names for identical params for different functions (e.g., "unit" vs "units")?

I guess a **kwargs could do, but we never use that (in public functions), so ...

[larsoner]

Can you give an example of what you are trying to do?

[larsoner]

Oh it is in the top post. I think the only clean way to fix it is to deprecate.