# naginterfaces.library.blas.dlangt¶

naginterfaces.library.blas.dlangt(norm, dl, d, du)[source]

dlangt returns the value of the -norm, the -norm, the Frobenius norm, or the maximum absolute value of the elements of a real tridiagonal matrix .

For full information please refer to the NAG Library document for f06rn

https://www.nag.com/numeric/nl/nagdoc_28.7/flhtml/f06/f06rnf.html

Parameters
normstr, length 1

Specifies the value to be returned.

or

The -norm.

The -norm.

or

The Frobenius (or Euclidean) norm.

The value (not a norm).

dlfloat, array-like, shape

The () subdiagonal elements of .

dfloat, array-like, shape

The diagonal elements of .

dufloat, array-like, shape

The () superdiagonal elements of .

Returns
nrmfloat

The value of the -norm, the -norm, the Frobenius norm, or the maximum absolute value of the elements of the real tridiagonal 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.