Master issue to make everything work with sparse matrices

[Zethson]

Description of feature

• Quality control
• normalization
• encoding -> sparse encoding #650
• [...]

[Zethson]

After trying your example, I either get “No columns detected” for automatic mode, or when I specify the column name (taken from subject.var.iloc[-1].name ) I get the error AttributeError: ‘csr_matrix’ object has no attribute ‘ravel’
wrong name?
my call is ep.pp.encode(subject, encodings={'one-hot': ['illness,_injury,_bereavement,_stress_in_last_2_years']})

encoding doesn't work for sparse matrices yet