LinearAlgebra`BLAS`
LinearAlgebra`BLAS`

# IAMAX

IAMAX[x]

gives the position of the element with the maximum absolute value in a vector x.

# Details and Options

• To use IAMAX, you first need to load the BLAS Package using Needs["LinearAlgebra`BLAS`"].
• The following argument must be given:
•  x input expression vector
• For complex vectors x, IAMAX locates the element with the greatest sum of absolute values of the real and imaginary parts.
• If x contains non-numeric elements, then IAMAX[x] always returns \$Failed.
• For duplicate entries the first position found is returned.

# Examples

open allclose all

## Basic Examples(1)

Find the position of the element with the largest absolute value in a vector:

## Scope(4)

A real vector:

A complex vector:

An arbitrary-precision vector:

Vectors with symbolic entries will return \$Failed:

## Properties & Relations(1)

IAMAX[x] is equivalent to Part[Position[Abs[x],Max[Abs[x]]],1,1] for real-valued vectors:

A similar relation is true for complex-valued vectors :

## Possible Issues(2)

If there are multiple elements with the same maximum absolute value, the position of the first one is returned:

If a vector contains a symbol, IAMAX returns \$Failed:

Wolfram Research (2017), IAMAX, Wolfram Language function, https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html.

#### Text

Wolfram Research (2017), IAMAX, Wolfram Language function, https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html.

#### CMS

Wolfram Language. 2017. "IAMAX." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html.

#### APA

Wolfram Language. (2017). IAMAX. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html

#### BibTeX

@misc{reference.wolfram_2023_iamax, author="Wolfram Research", title="{IAMAX}", year="2017", howpublished="\url{https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html}", note=[Accessed: 17-June-2024 ]}

#### BibLaTeX

@online{reference.wolfram_2023_iamax, organization={Wolfram Research}, title={IAMAX}, year={2017}, url={https://reference.wolfram.com/language/LowLevelLinearAlgebra/ref/IAMAX.html}, note=[Accessed: 17-June-2024 ]}