% plotj0:  creates a plot and finds the first n zeros of the bessel function J0
%
%  define the coordinate systems
%
z=0:.1:20;  % set z from 0 to 20
%%%
% define an "inline function for J0"
%%%
J0=inline('besselj(0,z)');  
%%%
% plot J0(z)
%%%
plot(z,J0(z)); grid;
xlabel('z');
title('J0(z)');
%%%%%%%%%%%%%%%%%%%%5
%  now find the first 3 zeros of Jm(z)  
%%%%%%%%%%%%%%%%%%%%%%
n=3;  %(find n zeros)
zguess=2 ; % estimate of first zero of J0
for i=1:n
  z0n(i)=fzero(J0,zguess);
  zguess=z0n(i)+3;
end
disp(sprintf('First %d zeros of J0 are',n));
z0n'