title: Plotting Bessel function in MATLAB
body: <p>In MATLAB how do you plot</p>
  
  <p>f(r) = { 2*J1(a*r) / r }^2</p>
  
  <p>where a = 2*pi
  and J1 is Bessel function of the 1st kind
  and r = sqrt(x^2 + y^2)</p>
  
  <p>This should plot in 3D, i.e. kind of be like a bubble (not sure how to do this)</p>