title: Matlab converting symbolic variable into array
body: <p>I want to convert a function that is defined in terms of a symbolic variable <code>x</code> into an array. My MWE is:</p>
  
  <pre><code>syms x
  f = x.^2;
  x = linspace(-10,10,100);
  f1 = double(f);
  </code></pre>
  
  <p>I tried to use the <code>double</code> command, but get an error</p>
  
  <pre><code>Error using symengine
  Unable to convert expression into double array.
  
  Error in sym/double (line 692)
          Xstr = mupadmex('symobj::double', S.s, 0);
  </code></pre>
  
  <p>I'm not sure what this means and how to resolve it.</p>