All about Matrix

Matrix multiplication

REMEMBER!

AB != BA ==> matrix multiplication is not commutative.
Cols in A == Rows in B (right, down)

Inverse

For a matrix M to have an inverse, it's determinant |M| != 0.

Given M is a 2x2 matrix.

m1 m2
m3 m4 = M

3 2
6 4 = M

det[M] = |M| = (m1)(m4) - (m2)(m3) = (3)(4) - (2)(6) = 0 _QED

!! Remember this arrowing only works till 3x3 matrix. Anything more will need to manually compute. Will come back to this.

Matrix inverse

M^-1 = 1/ |M| x (adjoint M)
... Crap... So hard to draw matrix. Ok Nvm. Come back to this later.

Mathworld Wolfram does a better job explaining it. Here: http://mathworld.wolfram.com/MatrixInverse.html


Ok... I should not spend so much time on this. Gotta hand in computer vision assignment in 10 days. Come back to this later.