title: how to evaluate derivative of function in matlab?
body: <p>This should be very simple. I have a function <code>f(x)</code>, and I want to evaluate <code>f'(x)</code> for a given <code>x</code> in MATLAB.</p>
  
  <p>All my searches have come up with symbolic math, which is not what I need, I need numerical differentiation.</p>
  
  <p>E.g. if I define: <code>fx = inline('x.^2')</code></p>
  
  <p>I want to find say <code>f'(3)</code>, which would be <code>6</code>, I don't want to find <code>2x</code></p>