AKEI0
This function evaluates the Kelvin function of the second kind, kei, of order zero.
Function Return Value
AKEI0 — Function value. (Output)
Required Arguments
X — Argument for which the function value is desired. (Input)
It must be nonnegative and less than 119.
FORTRAN 90 Interface
Generic: AKEI0 (X)
Specific: The specific interface names are S_AKEI0 and D_AKEI0.
FORTRAN 77 Interface
Single: AKEI0 (X)
Double: The double precision name is DKEI0.
Description
The modified Kelvin function kei0(x) is defined to be K0(xeπi4). The Bessel function K0(x) is defined in BSK0. Function AKEI0 is based on the work of Burgoyne (1963).
In AKEI0, x must satisfy 0  x < 119. If x < 0, then NaN (not a number) is returned. If x  119, then zero is returned.
Example
In this example, kei0(0.4) is computed and printed.
 
USE AKEI0_INT
USE UMACH_INT
 
IMPLICIT NONE
! Declare variables
INTEGER NOUT
REAL VALUE, X
! Compute
X = 0.4
VALUE = AKEI0(X)
! Print the results
CALL UMACH (2, NOUT)
WRITE (NOUT,99999) X, VALUE
99999 FORMAT (' AKEI0(', F6.3, ') = ', F6.3)
END
Output
 
AKEI0( 0.400) = -0.704