This function evaluates the Kelvin function of the first kind, ber, of order one.

Function Return Value

BER1 — Function value.   (Output)

Required Arguments

X — Argument for which the function value is desired.   (Input)

FORTRAN 90 Interface

Generic:                              BER1 (X)

Specific:                             The specific interface names are S_BER1 and D_BER1.

FORTRAN 77 Interface

Single:                                BER1 (X)

Double:                              The double precision name is DBER1.

Description

The Kelvin function ber1(x) is defined to be ℜJ1(xe3πi∕4). The Bessel function J1(x) is defined in BSJ1. Function BER1 is based on the work of Burgoyne (1963).

If |x| > 119, then NaN (not a number) is returned.

Example

In this example, ber1(0.4) is computed and printed.

 

      USE BER1_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 0.4

      VALUE = BER1(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' BER1(', F6.3, ') = ', F6.3)

      END

Output

 

BER1( 0.400) = -0.144

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