title: Symbolic summation in matlab
body: <p>I'm using MATLAB R2014b. I pasted code from example in documentation:
  <a href="https://www.mathworks.com/help/symbolic/symbolic-summation.html" rel="nofollow noreferrer">https://www.mathworks.com/help/symbolic/symbolic-summation.html</a></p>
  
  <pre><code>syms x
  assume(x &gt; 1)
  S_sum = sum(x.^(1:10))
  S_symsum = symsum(x^k, k, 1, 10)
  </code></pre>
  
  <p>and I got an error:</p>
  
  <pre><code>Undefined function or variable 'k'.
  
  Error in SymbolicExperience2 (line 4)
  S_symsum = symsum(x^k, k, 1, 10)
  </code></pre>
  
  <p>How do you think what's wrong? Should I migrate to MATLAB R2016b? Thank you.</p>