Add a sklearn.plot Module

Here is an overview of the work done so far relating to plotting:

• https://github.com/scikit-learn/scikit-learn/issues/8425 - Decision Regions of Classifiers
• https://github.com/scikit-learn/scikit-learn/pull/9173 - Confusion matrix and grid search
• https://github.com/scikit-learn/scikit-learn/issues/8425 - Calibration curve
• https://github.com/scikit-learn/scikit-learn/pull/12599 - Partial Dependence

To help control the scope of sklearn.plot, I propose we only do plotting on the axes level and not the figure level. The user would pass in the axes as a keyword. As a convenience, the default of axes will be None. Only in this case, will the plotting function generate a axes/figure to plot on.

[adrinjalali]

FWIW, I’d also prefer plot to inspect, since it’s more intuitive for most users to find it. People are more likely trying to plot their models than inspect their models (when searching on search engines for instance, or looking at the possible autocomplete options on their IDE).

[GaelVaroquaux]

IMO inspect is more versatile than plot

no strong opinion, will vote +1 for both name. Maybe plot is more straightforward?

“inspect” is loaded in Python (it’s a module in the standard library). I would avoid using the same name.

Again I’m interested in creating the new module before 0.21 and move plot_tree and plot_partial_dependence there. Ideally we should also reach consensus on the API (e.g., axes level/ figure level).

This shouldn’t delay 0.21. Our goal is to release early, and hopefully release early again.