###### tags: `Lecture2`
# lecture2_note

## KNN

kNN has a number of disadvantages:

- Very slow at test time
- Distance metrics on pixels are not informative

if will cause **"Curse of dimensionality"**：

## Linear classification

- xi has all of its pixels flattened out to a single column vector of shape [D x 1].
- The matrix W (of size [K x D])
- the vector b (of size [K x 1]) are the parameters of the function