BSK1
This function evaluates the modified Bessel function of the second kind of order one.
Function Return Value
BSK1 — Function value. (Output)
Required Arguments
X — Argument for which the function value is desired. (Input)
FORTRAN 90 Interface
Generic: BSK1 (X)
Specific: The specific interface names are S_BSK1 and D_BSK1.
FORTRAN 77 Interface
Single: BSK1 (X)
Double: The double precision function name is DBSK1.
Description
The Bessel function K1(x) is defined to be
The argument x must be large enough (> max(1/b, s)) that K1(x) does not overflow, and x must be small enough that the approximate answer,
does not underflow. Here, s is the smallest representable positive floating‑point number, s = AMACH(1) , and b = AMACH(2) is the largest representable floating‑point number.
Comments
Informational Error
Type | Code | Description |
|---|
2 | 1 | The function underflows because X is too large. |
Example
In this example, K1(0.5) is computed and printed.
USE BSK1_INT
USE UMACH_INT
IMPLICIT NONE
! Declare variables
INTEGER NOUT
REAL VALUE, X
! Compute
X = 0.5
VALUE = BSK1(X)
! Print the results
CALL UMACH (2, NOUT)
WRITE (NOUT,99999) X, VALUE
99999 FORMAT (' BSK1(', F6.3, ') = ', F6.3)
END
Output
BSK1( 0.500) = 1.656
