pairplot from Seaborn

[ChristopherDavisUCI]

Hi! I often find myself wishing there were a concise way in Altair to reproduce the pairplot function in Seaborn (or the similar scatterplot matrix in Plotly Express).

@joelostblom and I were talking about adding something like this in Altair. It would just be some shortcut I assume using the repeat operator. We would probably also add some additional Exploratory Data Analysis shortcut functions, along the lines of what @joelostblom has already written for Altair Ally.

Before we started on that (it's not a big priority), I wanted to check to see if there was any interest in having something like that on the Vega-Lite side. I don't know if these kind of shortcuts are in the spirit of Vega-Lite or not.

Thanks either way for any feedback!

[joelostblom]

I asked Dominik and Jeff about this and they mentioned that it is likely out of scope of Vega-Lite and would make more sense to add directly in Altair, so let's continue this discussion in vega/altair#2789 instead