Identity Matrix 單位矩陣

Identity Matrix / Unit Matrix 單位矩陣/恆等矩陣

Example:

I =
[ 1 0 ]
[ 0 1 ]

I =
[ 1 0 0 ]
[ 0 1 0 ]
[ 0 0 1 ]

I =
[ 1 0 0 0 ]
[ 0 1 0 0 ]
[ 0 0 1 0 ]
[ 0 0 0 1 ]

Matlab Example:

>> I = eye(4)

I =

     1     0     0     0
     0     1     0     0
     0     0     1     0
     0     0     0     1

>>

For an NxN identity matrix I and a NxN matrix A,

AI = IA = A

For an NxN identity matrix I and a Nx1 matrix B or a 1xN matrix C,

IB = B
CI = C

Reference:

Identity Matrix (Wikipedia/維基百科)