BSI1E
This function evaluates the exponentially scaled modified Bessel function of the first kind of order one.
Function Return Value
BSI1E — Function value. (Output)
Required Arguments
X — Argument for which the function value is desired. (Input)
FORTRAN 90 Interface
Generic: BSI1E (X)
Specific: The specific interface names are S_BSI1E and D_BSI1E.
FORTRAN 77 Interface
Single: BSI1E (X)
Double: The double precision function name is DBSI1E.
Description
Function
BSI1E computes e
−∣x∣ I1(
x). For the definition of the Bessel function
I1(
x), see
BSI1. The function
BSI1E underflows if
∣x∣/2 underflows.
Comments
Informational Error
Type | Code | Description |
|---|
2 | 1 | The function underflows because the absolute value of X is too small. |
Example
In this example, BSI1E(4.5) is computed and printed.
USE BSI1E_INT
USE UMACH_INT
IMPLICIT NONE
! Declare variables
INTEGER NOUT
REAL VALUE, X
! Compute
X = 4.5
VALUE = BSI1E(X)
! Print the results
CALL UMACH (2, NOUT)
WRITE (NOUT,99999) X, VALUE
99999 FORMAT (' BSI1E(', F6.3, ') = ', F6.3)
END
Output
BSI1E( 4.500) = 0.171
