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# hess

Hessenberg form

### Syntax

H = hess(A) [U,H] = hess(A)

### Arguments

- A
real or complex square matrix

- H
real or complex square matrix

- U
orthogonal or unitary square matrix

### Description

`[U,H] = hess(A)`

produces a unitary matrix
`U`

and a Hessenberg matrix `H`

so that
`A = U*H*U'`

and `U'*U`

=
Identity. By itself, `hess(A)`

returns `H`

.

The Hessenberg form of a matrix is zero below the first subdiagonal. If the matrix is symmetric or Hermitian, the form is tridiagonal.

### References

hess function is based on the Lapack routines DGEHRD, DORGHR for real matrices and ZGEHRD, ZORGHR for the complex case.

### See also

### Used Functions

`hess`

function is based on the Lapack routines
DGEHRD, DORGHR for real matrices and ZGEHRD, ZORGHR for the
complex case.

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