Convert math equations to numpy

This is a memo for coding matrix operations in numpy.

Hadamard product

A*B

Matrix multiplication

np.dot(A, B)
np.matmul(A, B)
A @ B

Outer product

np.outer(A, B)

Kronecker product

np.kron(A, B)

if a and b are vectors, the Kronecker product is a form of vectorization (or flattening) of the outer product of a and b.

np.kron(a, b) == np.outer(a, b).reshape(-1)

All images are retrieved from Wikipedia.