# Tag Info

When you talk about 1x3 or 3x1, we do not know if you are talking about COLxROW or ROWxCOL. The typical way of representing a vector in a matrix is ROWxCOL terms, so 3x1 is what you are looking for The matrix multiplication uses a single column with $N$ entries multiplied by an $N*N$ matrix. Since this is multiplication the order does not matter, $P*K$ is ...