# naginterfaces.library.blas.dsrotg¶

naginterfaces.library.blas.dsrotg(pivot, direct, alpha, x)[source]

dsrotg generates a sequence of real plane rotations.

For full information please refer to the NAG Library document for f06fq

https://www.nag.com/numeric/nl/nagdoc_29.2/flhtml/f06/f06fqf.html

Parameters
pivotstr, length 1

Specifies the plane rotated by .

(variable pivot)

rotates the plane.

(fixed pivot)

rotates the plane if , or the plane if .

directstr, length 1

Specifies the sequence direction.

(forward sequence)

.

(backward sequence)

.

alphafloat

The scalar .

xfloat, array-like, shape

The -element vector .

Returns
alphafloat

The scalar .

xfloat, ndarray, shape

The referenced elements are overwritten by details of the sequence of plane rotations.

cfloat, ndarray, shape

The values , the cosines of the rotations.

sfloat, ndarray, shape

The values , the sines of the rotations.

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(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.

dsrotg generates the parameters of a real orthogonal matrix , of order , chosen so as to set to zero the elements of a supplied -element real vector .

If and , or if and ,

If and , or if and ,

Here and are real scalars.

is represented as a sequence of plane rotations , as specified by and ; is chosen to annihilate , and its plane rotation part has the form

The tangent of the rotation, , is overwritten on .