scikit-learn/scikit-learn — comment on commit 6d5cb365cc4ec6f7057bd2d2ad07043fe916d2af
File: doc/modules/linear_model.rst line 30
By ogrisel:

I don't think there is a general notation for the number of features in ML (also statisticians are probably using `p` more often than not). In the ML literature you also often encounter `n` when `m` or `N` is the number of samples or even `d` (for "dimensions").