Discsusion/Feature request: subplot-managed axis labels

When drawing “small multiples” — a grid of subplots where each uses the same x and y variables — it can be cleaner to use a pair of labels that collectively annotate the x and y axes of all plots, ideally centered on the horizontal and vertical span of the collection of axes.

Here’s what I mean:


I don’t believe matplotlib has a robust and generic way to create these labels. In the above example, I set the axes-level labels for the middle row/column, which only works when ncol and nrow are odd. It could be possible to get the SubplotSpec bbox and work out where to draw fig.text labels, but I don’t think these will update properly with tight_layout/constrained_layout.

Would it be possible for the matplotlib.gridspec.SubplotSpec object to define {get,set}_{x,y}label? How hard would this be to implement? Is there interest?

PS I guess people might reasonably expect subplot-managed titles too. And legends? I can see how this request might get out of hand. Then again, all of these features would be useful if there are abstractions that can make them not too burdensome.

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Thats a reasonable request. See https://github.com/matplotlib/matplotlib/issues/11147 for previous discussion, and https://github.com/matplotlib/matplotlib/pull/13072 for the same thing for legends. We already have suptitle, but it is on a figure basis.

I agree that this should go at the gridspec level, and then they can be nested.

I think this would be easy to implement with constrained_layout, though gridspec-level decorators are kind of a sticking point right now. suptitle is special cased, and its relatively trivial in constrained_layout.