s18aff

s18aff © Numerical Algorithms Group, 2002.

Purpose

S18AFF Modified Bessel function I (x) 1

Synopsis

[fun_value,ifail] = s18aff(x<,ifail>)

Description

 
 This routine evaluates an approximation to the modified Bessel 
 Function of the first kind I (x).
                             1   
 
 Note: I (-x)=-I (x), so the approximation need only consider 
        1       1                                             
 x>=0.
 
 For large x, the routine must fail because I (x) cannot be 
                                             1             
 represented without overflow.

Parameters

s18aff

Required Input Arguments:

x                                     real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

ifail                                 integer