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 kei
0(
x) is defined to be
ℑK0(
xeπi∕4). 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
