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# obsv

Observability matrix

obsv(A,C)
Ob = obsv(sys)

## Description

obsv computes the observability matrix for state-space systems. For an n-by-n matrix A and a p-by-n matrix C, obsv(A,C) returns the observability matrix

with n columns and np rows.

Ob = obsv(sys) calculates the observability matrix of the state-space model sys. This syntax is equivalent to executing

```Ob = obsv(sys.A,sys.C)
```

The model is observable if Ob has full rank n.

## Examples

Determine if the pair

```A =
1     1
4    -2

C =
1     0
0     1
```

is observable. Type

```Ob = obsv(A,C);

% Number of unobservable states
unob = length(A)-rank(Ob)
```

These commands produce the following result.

```unob =
0
```