unobs

unobs — unobservable subspace

Calling sequence

[n,[U]]=unobs(A,C,[tol])

`A, C`	: real matrices
`tol`	: tolerance used when evaluating ranks (QR factorizations).
`n`	: dimension of unobservable subspace.
`U`	: orthogonal change of basis which puts `(A,B)` in canonical form.

[n,[U]]=unobs(A,C,[tol]) gives the unobservable form of an (A,C) pair. The n first columns of U make a basis for the unobservable subspace.

The (2,1) block (made of last nx-n rows and n first columns) of U'*A*U is zero and and the n first columns of C*U are zero.



A=diag([1,2,3]);C=[1,0,0];
unobs(A,C)