# obsv

Returns the observability matrix of a state-space model.

OB = obsv(SYS)

OB = obsv(A, C)

## Inputs

SYS
Continuous-time state-space model.
A
The state matrix (n x n), where n is the number of states.
C
The output matrix (q x n), where q is the number of outputs.

## Outputs

OB
The observability matrix.

## Examples

Observability matrix from state matrices:
A = [10  1;3 -5];
C = [5  0;0  6];
R = obsv(A, C)
R1 = length(A) - rank(R)    % number of unobservable states
 R = [Matrix] 4 x 2
5    0
0    6
50    5
18  -30

R1 = 0
Observability matrix from a transfer function model:
sys_tf = tf([1],[2 9 3]);
sys = ss(sys_tf);
R2 = obsv(sys)
 R2 = [Matrix] 2 x 2
0  1
1  0