naginterfaces.library.blas.izamax

naginterfaces.library.blas.izamax(x)

izamax computes the index of the absolutely largest component of a complex vector.

For full information please refer to the NAG Library document for f06jm

https://www.nag.com/numeric/nl/nagdoc_29.3/flhtml/f06/f06jmf.html

Parameters

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

The $n$-element vector $x$.

Returns

imaxint

The index of the absolutely largest component of a complex vector, $x$.

Raises

NagValueError

(errno $3$)

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

Constraint: $\text{incx}>0$.

Notes

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

izamax returns the smallest index $i$ such that

$$\left|Re\left(x_i\right)\right|+\left|Im\left(x_i\right)\right|={max}_j(\left|Re\left(x_j\right)\right|+\left|Im\left(x_j\right)\right|)$$

where $x$ is an $n$-element complex vector.

References

Lawson, C L, Hanson, R J, Kincaid, D R and Krogh, F T, 1979, Basic linear algebra supbrograms for Fortran usage, ACM Trans. Math. Software (5), 308–325