Chapter 6: Bessel Functions

CBJS

Evaluates a sequence of Bessel functions of the first kind with real order and complex arguments.

Required Arguments

XNU — Real argument which is the lowest order desired.   (Input)
XNU must be greater than −1/2.

Z — Complex argument for which the sequence of Bessel functions is to be evaluated.   (Input)

N — Number of elements in the sequence.   (Input)

CBS — Vector of length N containing the values of the function through the series.   (Output)
CBS(I) contains the value of the Bessel function of order XNU + I − 1 at Z for I = 1
to N.

FORTRAN 90 Interface

Generic:                              CALL CBJS (XNU, Z, N, CBS)

Specific:                             The specific interface names are S_CBJS and D_CBJS.

FORTRAN 77 Interface

Single:                                cALL CBJS (XNU, Z, N, CBS)

Double:                              The double precision name is DCBJS.

Description

The Bessel function Jν(z) is defined to be

This code is based on the code BESSCC of Barnett (1981) and Thompson and Barnett (1987).

This code computes Jν(z) from the modified Bessel function Iν(z), CBIS, using the following relation, with ρ = ei π2:

Comments

Informational error

Type Code

3         1                  One of the continued fractions failed.

4         2                  Only the first several entries in CBS are valid.

Example

In this example, J0.3+ ν1(1.2 + 0.5i), ν= 1, …, 4 is computed and printed.

 

      USE CBJS_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    N

      PARAMETER  (N=4)

!    

      INTEGER    K, NOUT

      REAL       XNU

      COMPLEX    CBS(N), Z

!                                 Compute

      XNU = 0.3

      Z   = (1.2, 0.5)

      CALL CBJS (XNU, Z, N, CBS)

!                                 Print the results

      CALL UMACH (2, NOUT)

      DO 10  K=1, N

         WRITE (NOUT,99999) XNU+K-1, Z, CBS(K)

   10 CONTINUE

99999 FORMAT (' J sub ', F6.3, ' ((', F6.3, ',', F6.3, &

           ')) = (', F9.3, ',', F9.3, ')')

      END

Output

 

 J sub  0.300 (( 1.200, 0.500)) = (    0.774,   -0.107)

 J sub  1.300 (( 1.200, 0.500)) = (    0.400,    0.159)

 J sub  2.300 (( 1.200, 0.500)) = (    0.087,    0.092)

 J sub  3.300 (( 1.200, 0.500)) = (    0.008,    0.024)



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