This function evaluates the Bessel function of the first kind of order zero.

Function Value Return

BSJ0 — Function value.   (Output)

Required Arguments

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

FORTRAN 90 Interface

Generic:             BSJ0 (X)

Specific:                             The specific interface names are S_BSJ0 and D_BSJ0.

FORTRAN 77 Interface

Single:              BSJ0 (X)

Double:                              The double precision function name is DBSJ0.

Description

The Bessel function J0(x) is defined to be

To prevent the answer from being less accurate than half precision, |x| should be smaller than

For the result to have any precision at all, |x| must be less than 1/ε. Here, ε is the machine precision, ε = AMACH(4).

Figure 6- 1  Plot of J0(x) and J1(x)

Example

In this example, J0(3.0) is computed and printed.

 

      USE BSJ0_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 3.0

      VALUE = BSJ0(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' BSJ0(', F6.3, ') = ', F6.3)

      END

Output

 

BSJ0( 3.000) = -0.260

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