s17adf

Purpose

Synopsis

[fun_value,ifail] = s17adf(x<,ifail>)

Description

 
 This routine evaluates an approximation to the Bessel Function of
 the second kind Y (x).
                  1   
 
 Note: Y (x) is undefined for x<=0 and the routine will fail for 
        1                                                       
 such arguments.
                             2                                   
 For x near zero, Y (x)~=- -----. This approximation is used when 
                   1       (pi)x                                 
 x is sufficiently small for the result to be correct to machine 
 precision. For extremely small x, there is a danger of overflow 
                    2                                          
 in calculating - ----- and for such arguments the routine will 
                  (pi)x                                        
 fail.
 
 For very large x, it becomes impossible to provide results with 
 any reasonable accuracy, hence the routine fails. Such arguments 
 contain insufficient information to determine the phase of 
                                               ______ 
                                              /   2   
 oscillation of Y (x), only the amplitude,   /  -----, can be 
                 1                         \/   (pi)x 
 determined and this is returned on soft failure. The range for 
 which this occurs is roughly related to machine precision; the 
 routine will fail if x>~1/machine precision.
 

Parameters

s17adf

Required Input Arguments:

x                                     real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

ifail                                 integer