naginterfaces.library.matop.dtrttp

naginterfaces.library.matop.dtrttp(uplo, a)

dtrttp copies a real triangular matrix, stored in a full format array, to a standard packed format array.

For full information please refer to the NAG Library document for f01va

https://support.nag.com/numeric/nl/nagdoc_30.3/flhtml/f01/f01vaf.html

Parameters

uplostr, length 1

Specifies whether $A$ is upper or lower triangular.

$uplo=\text{'U'}$

$A$ is upper triangular.

$uplo=\text{'L'}$

$A$ is lower triangular.

afloat, array-like, shape $(n,n)$

The triangular matrix $A$.

Returns

apfloat, ndarray, shape $(n\times (n+1)/2)$

The $n\times n$ triangular matrix $A$, packed by columns.

Raises

NagValueError

(errno $-1$)

On entry, error in parameter $uplo$.

Constraint: $uplo=\text{'U'}$ or $\text{'L'}$.

(errno $-2$)

On entry, error in parameter $\text{n}$.

Constraint: $n\ge 0$.

Notes

dtrttp packs a real $n\times n$ triangular matrix $A$, stored conventionally in a full format array, into an array of length $n(n+1)/2$. The matrix is packed by columns. This function is intended for possible use in conjunction with functions from submodule blas, submodule blast, submodule lapacklin and submodule lapackeig where some functions use triangular matrices stored in the packed form. Packed storage format is described in the F07 Introduction.