naginterfaces.library.blas.dnrm2w

naginterfaces.library.blas.dnrm2w(w, x)

dnrm2w computes the weighted Euclidean norm of a real vector.

For full information please refer to the NAG Library document for f06fk

https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f06/f06fkf.html

Parameters

wfloat, array-like, shape $\left(n\right)$

$w$, the vector of weights.

xfloat, array-like, shape $\left(n\right)$

The $n$-element vector $x$.

Returns

nrmfloat

The weighted Euclidean norm of the real vector, $x$.

Raises

NagValueError

(errno $2$)

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

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

Notes

No equivalent traditional C interface for this routine exists in the NAG Library.

dnrm2w returns the weighted Euclidean norm

$$\sqrt{x^{T}Wx}$$

of the $n$-element real vector $x$, where $W=diag\left(w\right)$ and $w$ is a vector of weights.