s18def

Purpose

Synopsis

[cy,nz,ifail] = s18def(fnu,z,n<,scale,ifail>)

Description

 
 This subroutine evaluates a sequence of values for the modified 
 Bessel function I    (z), where z is complex, -(pi) < argz <= 
                  (nu)                                        
 (pi), and (nu) is the real, non-negative order. The N-member 
 sequence is generated for orders (nu), (nu)+1,...,(nu)+N-1. 
                                                   -|Rez|
 Optionally, the sequence is scaled by the factor e      .
 
 The routine is derived from the routine CBESI in Amos [2].
 
 Note: although the routine may not be called with (nu) less than 
 zero, for negative orders the formula 
                      2                                        
 I     (z)=I    (z)+ ----sin((pi)(nu))K    (z) may be used (for 
  -(nu)     (nu)     (pi)              (nu)                    
 the Bessel function K    (z), see S18DCF).
                      (nu)                
 
 When N is greater than 1, extra values of I    (z) are computed 
                                            (nu)                
 using recurrence relations.
 
 For very large |z| or ((nu)+N-1), argument reduction will cause 
 total loss of accuracy, and so no computation is performed. For 
 slightly smaller |z| or ((nu)+N-1), the computation is performed 
 but results are accurate to less than half of machine precision. 
 If Re(z) is too large and the unscaled function is required, 
 there is a risk of overflow and so no computation is performed. 
 In all the above cases, a warning is given by the routine.
 

Parameters

s18def

Required Input Arguments:

fnu                                   real
z                                     complex
n                                     integer

Optional Input Arguments:                       <Default>

scale (1)                             string   'u'
ifail                                 integer  -1

Output Arguments:

cy (n)                                complex
nz                                    integer
ifail                                 integer