---
name: "iamax"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/iamax"
---

# iamax(3)

iamax: argmax\_i \| real( x\_i ) \| + \| imag( x\_i ) \|

## NAME

iamax - iamax: argmax\_i \| real( x\_i ) \| + \| imag( x\_i ) \|

## SYNOPSIS

### Functions

integer function **icamax** (n, cx, incx)\
 **ICAMAX**  integer function **idamax** (n, dx, incx)\
 **IDAMAX**  integer function **isamax** (n, sx, incx)\
 **ISAMAX**  integer function **izamax** (n, zx, incx)\
 **IZAMAX**

## Detailed Description

## Function Documentation

### integer function icamax (integer n, complex, dimension(\*) cx, integer incx)

**ICAMAX**

**Purpose:**

```
!>
!>    ICAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>         number of elements in input vector(s)
!>
```

*CX*

```
!>          CX is COMPLEX array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
!>
```

*INCX*

```
!>          INCX is INTEGER
!>         storage spacing between elements of CX
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>     jack dongarra, linpack, 3/11/78.
!>     modified 3/93 to return if incx .le. 0.
!>     modified 12/3/93, array(1) declarations changed to array(*)
!>
```

Definition at line **70** of file **icamax.f**.

### integer function idamax (integer n, double precision, dimension(\*) dx, integer incx)

**IDAMAX**

**Purpose:**

```
!>
!>    IDAMAX finds the index of the first element having maximum absolute value.
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>         number of elements in input vector(s)
!>
```

*DX*

```
!>          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
!>
```

*INCX*

```
!>          INCX is INTEGER
!>         storage spacing between elements of DX
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>     jack dongarra, linpack, 3/11/78.
!>     modified 3/93 to return if incx .le. 0.
!>     modified 12/3/93, array(1) declarations changed to array(*)
!>
```

Definition at line **70** of file **idamax.f**.

### integer function isamax (integer n, real, dimension(\*) sx, integer incx)

**ISAMAX**

**Purpose:**

```
!>
!>    ISAMAX finds the index of the first element having maximum absolute value.
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>         number of elements in input vector(s)
!>
```

*SX*

```
!>          SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
!>
```

*INCX*

```
!>          INCX is INTEGER
!>         storage spacing between elements of SX
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>     jack dongarra, linpack, 3/11/78.
!>     modified 3/93 to return if incx .le. 0.
!>     modified 12/3/93, array(1) declarations changed to array(*)
!>
```

Definition at line **70** of file **isamax.f**.

### integer function izamax (integer n, complex\*16, dimension(\*) zx, integer incx)

**IZAMAX**

**Purpose:**

```
!>
!>    IZAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>         number of elements in input vector(s)
!>
```

*ZX*

```
!>          ZX is COMPLEX*16 array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
!>
```

*INCX*

```
!>          INCX is INTEGER
!>         storage spacing between elements of ZX
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>     jack dongarra, 1/15/85.
!>     modified 3/93 to return if incx .le. 0.
!>     modified 12/3/93, array(1) declarations changed to array(*)
!>
```

Definition at line **70** of file **izamax.f**.

## Author

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