Two matrices can be multiplied
together only when
the number of columns in the matrix on the left equals the number of rows in
the matrix on the right.
For example, suppose
- matrix A is N x M
- matrix B is L x R
The matrix product AB is
only defined in M = L.
matrix will be of size N x R.
It is performed by multiplying each
row of A by each column of B
are terms for describing the order of matrix multiplication
a matrix appears on the left, it is pre-multiplied.
a matrix appears on the right, it is post-multiplied.
example, in the matrix product AB
- A is pre-multiplied to B
- B is post-multiplied to A