evaluate bessel with plot

Hi, i wonder if anyone can help on why i receive this error "??? Error using ==> plot Vectors must be the same lengths"

I want to plot a function of combination of differentiation of bessel.

m=0; k=0; omega=0:0.02:10; 

a = besselj(m,omega);
da = diff(a);

b = bessely(k,omega);
db = diff(b);

c = besselj(m,omega);
dc = diff(c);

d = bessely(k,omega);
dd = diff(d);

g=da.*dd-dc.*db;

plot(omega,g); 
hold all; 
plot(omega,0,'k'); 
axis([min(omega) max(omega) -100 100]);

thanks so much

Answer 1

[Walter Roberson]

Your arguments to the the bessel functions are numeric, so you are using the numeric bessel functions and getting numeric answers. diff() applied to a numeric vector is the difference function (not differentiation) and results in a vector that is one shorter than the original. You then attempt to plot the original-length omega vector against the one-shorter difference vector.