AKEIP0

AKEIP0

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

Function Return Value

AKEIP0 — Function value. (Output)

Required Arguments

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

FORTRAN 90 Interface

Generic: AKEIP0 (X)

Specific: The specific interface names are S_AKEIP0 and D_AKEIP0.

FORTRAN 77 Interface

Single: AKEIP0 (X)

Double: The double precision name is DKEIP0.

Description

The function keiʹ0(x) is defined to be

where kei0(x) is a Kelvin function, see AKEI0. Function AKEIP0 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, keiʹ0(0.6) is computed and printed.

USE AKEIP0_INT

USE UMACH_INT

IMPLICIT NONE

! Declare variables

INTEGER NOUT

REAL VALUE, X, AKEIP0

! Compute

X = 0.6

VALUE = AKEIP0(X)

! Print the results

CALL UMACH (2, NOUT)

WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' AKEIP0(', F6.3, ') = ', F6.3)

END

Output

AKEIP0( 0.600) = 0.348