NAG Library Routine Document

F06FLF

+− Contents

1 Purpose

9 Example

F06FLF returns the absolutely largest and absolutely smallest values from a real vector.

SUBROUTINE F06FLF (

INTEGER	N, INCX
REAL (KIND=nag_wp)	X(*), XMAX, XMIN

F06FLF returns the values

x_{\max}

and

x_{\min}

given by

x_{\max} = \max_{i} |x_{i}|, x_{\min} = \min_{i} |x_{i}|,

where

x

is an

n

-element real vector scattered with stride INCX. If

n < 1

, then

x_{\max}

and

x_{\min}

are returned as zero.

None.

1: N – INTEGERInput: On entry: $n$ , the number of elements in $x$ .
2: X( $*$ ) – REAL (KIND=nag_wp) arrayInput: Note: the dimension of the array X must be at least $\max (1, 1 + (N - 1) \times INCX)$ .
On entry: the $n$ -element vector $x$ . $x_{i}$ must be stored in $X (1 + (i - 1) \times INCX)$ , for $i = 1, 2, \dots, N$ .
Intermediate elements of X are not referenced.
3: INCX – INTEGERInput: On entry: the increment in the subscripts of X between successive elements of $x$ .
Constraint: $INCX > 0$ .
4: XMAX – REAL (KIND=nag_wp)Output: On exit: the value $x_{\max} = \max_{i} |x_{i}|$ .
5: XMIN – REAL (KIND=nag_wp)Output: On exit: the value $x_{\min} = \min_{i} |x_{i}|$ .