# naginterfaces.library.blas.dutsrh¶

naginterfaces.library.blas.dutsrh(side, k1, k2, c, s, a)[source]

dutsrh transforms a real upper triangular matrix to an upper Hessenberg matrix by applying a given sequence of plane rotations.

For full information please refer to the NAG Library document for f06qv

https://www.nag.com/numeric/nl/nagdoc_28.7/flhtml/f06/f06qvf.html

Parameters
sidestr, length 1

Specifies whether is operated on from the left or the right.

is pre-multiplied from the left.

is post-multiplied from the right.

k1int

The value .

k2int

The value .

cfloat, array-like, shape

must hold , the cosine of the rotation , for .

sfloat, array-like, shape

must hold , the sine of the rotation , for .

afloat, array-like, shape

The upper triangular matrix .

Returns
sfloat, ndarray, shape

holds , the subdiagonal element of , for .

afloat, ndarray, shape

The upper triangular part of the upper Hessenberg matrix .

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(errno )

On entry, error in parameter .

Constraint: .

Notes

No equivalent traditional C interface for this routine exists in the NAG Library.

dutsrh transforms an real upper triangular matrix to an upper Hessenberg matrix , by applying a given sequence of plane rotations from either the left or the right, in planes to ; has nonzero subdiagonal elements , for only.

If , the rotations are applied from the left:

where .

If , the rotations are applied from the right:

where .

In either case, is a rotation in the plane.

The plane rotation part of has the form