ion.

There are two straight-forward ways to reduce multi-class to binary classification.
the first is called one vs rest, the second one is called one-vs-one.

---
class: spacious

# One Vs Rest

For 4 classes:

1v{2,3,4}, 2v{1,3,4}, 3v{1,2,4}, 4v{1,2,3}

In general:

n binary classifiers - each on all data

???
Let's start with One vs Rest.
here, we learn one binary classifier for each class against the remaining
classes. So let's say we have 4 classes, called 1 to 4.  First we learn a
binary classifier o