AKEI1

AKEI1

This function evaluates the Kelvin function of the second kind, kei, of order one.

Function Return Value

AKEI1 — Function value. (Output)

Required Arguments

X — Argument for which the function value is desired. (Input)
It must be nonnegative.

FORTRAN 90 Interface

Generic: AKEI1 (X)

Specific: The specific interface names are S_AKEI1 and D_AKEI1.

FORTRAN 77 Interface

Single: AKEI1 (X)

Double: The double precision name is DKEI1.

Description

The modified Kelvin function kei1(x) is defined to be

. The Bessel function K1(x) is defined in BSK1. Function AKEI1 is based on the work of Burgoyne (1963).

If x < 0, then NaN (not a number) is returned. If x ≥ 119, then zero is returned.

Example

In this example, kei1(0.4) is computed and printed.

USE UMACH_INT

USE AKEI1_INT

IMPLICIT NONE

! Declare variables

INTEGER NOUT

REAL VALUE, X

! Compute

X = 0.4

VALUE = AKEI1(X)

! Print the results

CALL UMACH (2, NOUT)

WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' AKEI1(', F6.3, ') = ', F6.3)

END

Output

AKEI1( 0.400) = -1.444