function In = besin(nn,x)
% BESIN Bessel function I(x) for integer and fractional order.
%
%	I = BESIN(N,X) Bessel function I(X) for integer/fractional order N 
%       NOTE: N must be a scalar.
%
%	NOTE: For a definition, see Abramowitz and Stegun
%
%       BESIN (with no input arguments) invokes the following example:
%
%	% Compute I(x) of order 3 for xx = [1 2 3 4 5]
%	  >>xx = 1:5
%         >>Ixx = besin(3,xx)


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: akambard@mtu.edu
% Copyright (c) 1998



if nargin==0,help besin,disp('strike a key to see results of the example')
pause,xx=1:5,Ixx=besin(3,xx),return,end

if exist('besseli')==2, In = besseli(nn,x);return,end

tol=2e-16;
z=x+(x==0);n=nn;
if round(n) == n, n=abs(n);end
In=exp(n*lnn(z/2)).*ghgf(0,1,[1 1 1 1],[n+1 1 1 1],(z.*z)/4,tol)/gm(n+1);
In=In.*(x~=0)+(x==0 & n==0);