title: How to find the roots of a polynomial within a given interval
body: <p>I want to write a function with inputs of a polynomial (p), and a range (a, b), which gives the number of the roots of a polynomial in this range. But I don't know how to set the range in the function.</p>
  
  <pre><code>x=poly(0,"x")
  a = 0;
  b = 5;
  p=-6+11*x-6*x^2+x^3
  
  function [n_roots] = numroots (p,a,b)
      rootn = roots(p)
  //todo
      n_roots = length(rootn)
  endfunction
  </code></pre>
  
  <p>The next step will be represent the polynomial and the roots in a graph.</p>