BER1

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