naginterfaces.library.blas.dutr1¶
- naginterfaces.library.blas.dutr1(alpha, x, y, a)[source]¶
dutr1
performs a factorization (as a sequence of plane rotations) of a real upper triangular matrix that has been modified by a rank-1 update.For full information please refer to the NAG Library document for f06qp
https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f06/f06qpf.html
- Parameters
- alphafloat
The scalar .
- xfloat, array-like, shape
The -element vector .
- yfloat, array-like, shape
The -element vector .
- afloat, array-like, shape
The upper triangular matrix .
- Returns
- xfloat, ndarray, shape
The referenced elements are overwritten by details of the sequence of plane rotations.
- afloat, ndarray, shape
The upper triangular matrix .
- cfloat, ndarray, shape
The cosines of the rotations , for .
- sfloat, ndarray, shape
The sines of the rotations , for .
- Raises
- NagValueError
- (errno )
On entry, error in parameter .
Constraint: .
- (errno )
On entry, error in parameter .
Constraint: .
- (errno )
On entry, error in parameter .
Constraint: .
- Notes
No equivalent traditional C interface for this routine exists in the NAG Library.
dutr1
performs a factorization of an upper triangular matrix which has been modified by a rank-1 update:where and are real upper triangular matrices, and are -element real vectors, is a real scalar, and is an real orthogonal matrix.
is formed as the product of two sequences of plane rotations:
where
is a rotation in the plane, chosen to annihilate : thus , where and is the last column of the unit matrix;
is a rotation in the plane, chosen to annihilate the element of , and thus restore it to upper triangular form.
The plane rotation part of or has the form
The tangents of the rotations are returned in the array ; the cosines and sines of these rotations can be recovered by calling
dcsg()
. The cosines and sines of the rotations are returned directly in the arrays and .