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

Function Return Value

AKER1 — Function value.   (Output)

Required Arguments

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

FORTRAN 90 Interface

Generic:                              AKER1 (X)

Specific:                             The specific interface names are S_AKER1 and D_AKER1.

FORTRAN 77 Interface

Single:                                AKER1 (X)

Double:                              The double precision name is DKER1.

Description

The modified Kelvin function ker1(x) is defined to be . The Bessel function K1(x) is defined in BSK1. Function AKER1 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, ker1(0.4) is computed and printed.

 

      USE AKER1_INT
      USE UMACH_INT

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 0.4

      VALUE = AKER1(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' AKER1(', F6.3, ') = ', F6.3)

      END

Output

 

AKER1( 0.400) = -1.882

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