s17dcf
s17dcf
© Numerical Algorithms Group, 2002.
Purpose
S17DCF Bessel functions Y (z), real a >= 0, complex z,
nu + a
nu = 0,1,2,...
Synopsis
[cy,nz,ifail] = s17dcf(fnu,z,n<,scale,ifail>)
Description
This subroutine evaluates a sequence of values for the Bessel
function Y (z), where z is complex, -(pi) < arg z <= (pi), and
(nu)
(nu) is the real, non-negative order. The N-member sequence is
generated for orders (nu), (nu)+1,...,(nu)+N-1. Optionally, the
-|Im z|
sequence is scaled by the factor e .
Note: although the routine may not be called with (nu) less than
zero, for negative orders the formula
Y (z)=Y (z)cos((pi)(nu))+J (z)sin((pi)(nu)) may be used
-(nu) (nu) (nu)
(for the Bessel function J (z), see S17DEF).
(nu)
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 |z| is very small, near the machine underflow threshold, or
((nu)+N-1) is too large, 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
s17dcf
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