UNOBS(G)

NAME
unobs - unobservable subspace

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

PARAMETERS

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.

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

SEE ALSO
contr, contrss, canon, cont_mat, spantwo