What is the dimension of the pseudo inverse of a m x n matrix ?
If A is an m x n matrix, then system:
A*x = b
can not be solved by inverse A. You have to do
A' A x = A' b
and then, x = inv(A' A) A' b
so pinv(A) is defined as inv(A' A) * A', which means pinv(A) will be a n x m matrix.