BSJ0
This function evaluates the Bessel function of the first kind of order zero.
Function Return Value
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/ɛ. Here, ɛ is the machine precision, ɛ = AMACH(4).
Figure 11, 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
