Function: BESSEL
Purpose: Evaluate Bessel function J, Y, I, K of integer order.
Category: MATH
File: bessel.c
Author: M.G.R. Vogelaar
Use: See bessj.dc2, bessy.dc2, bessi.dc2 or bessk.dc2
Description: The differential equation
2
2 d w dw 2 2
x . --- + x . --- + (x - v ).w = 0
2 dx
dx
has two solutions called Bessel functions of the first kind
Jv(x) and Bessel functions of the second kind Yv(x).
The routines bessj and bessy return the J and Y for
integer v and therefore are called Bessel functions
of integer order.
The differential equation
2
2 d w dw 2 2
x . --- + x . --- - (x + v ).w = 0
2 dx
dx
has two solutions called modified Bessel functions
Iv(x) and Kv(x).
The routines bessi and bessk return the I and K for
integer v and therefore are called Modified Bessel
functions of integer order.
(Abramowitz & Stegun, Handbook of mathematical
functions, ch. 9, pages 358,- and 374,- )
The implementation is based on the ideas from
Numerical Recipes, Press et. al.
This routine is NOT callable in FORTRAN.
Updates: Jun 29, 1998: VOG, Document created.