s18adf

s18adf © Numerical Algorithms Group, 2002.

Purpose

S18ADF Modified Bessel function K (x) 1

Synopsis

[fun_value,ifail] = s18adf(x<,ifail>)

Description

 
 This routine evaluates an approximation to the modified Bessel 
 Function of the second kind K (x).
                              1   
 
 Note: K (x) is undefined for x<=0 and the routine will fail for 
        1                                                       
 such arguments.

                          1 
 For x near zero, K (x)~= -. This approximation is used when x is 
                   1      x                                      
 sufficiently small for the result to be correct to machine 
 precision. For very small x on some machines, it is impossible to
            1                                       
 calculate  - without overflow and the routine must fail.
            x                                       
 

Parameters

s18adf

Required Input Arguments:

x                                     real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

ifail                                 integer