# naginterfaces.library.lapackeig.ddisna¶

naginterfaces.library.lapackeig.ddisna(job, m, n, d)[source]

ddisna computes the reciprocal condition numbers for the eigenvectors of a real symmetric or complex Hermitian matrix , or for the left or right singular vectors of a general matrix .

For full information please refer to the NAG Library document for f08fl

https://www.nag.com/numeric/nl/nagdoc_28.7/flhtml/f08/f08flf.html

Parameters
jobstr, length 1

Specifies for which problem the reciprocal condition number should be computed.

The eigenvectors of a symmetric or Hermitian matrix.

The left singular vectors of a general matrix.

The right singular vectors of a general matrix.

mint

, the number of rows of the matrix .

nint

, the number of columns of the matrix when or .

If , is not referenced.

dfloat, array-like, shape

Note: the required length for this argument is determined as follows: if : ; if : ; otherwise: .

The eigenvalues if , or singular values if or of the matrix .

Returns
sepfloat, ndarray, shape

The reciprocal condition numbers of the vectors.

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: , or .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: the elements of the array must be in increasing or decreasing order.

(errno )

On entry, error in parameter .

Constraint: the elements of the array must not be negative.

Notes

The bound on the error, measured by the angle in radians, for the th computed vector is given by , where is the machine precision and is the reciprocal condition number for the vectors, returned in the array element . is restricted to be at least in order to limit the size of the error bound.

References

Golub, G H and Van Loan, C F, 1996, Matrix Computations, (3rd Edition), Johns Hopkins University Press, Baltimore