title: How to concatenate string cell contents
body: <p>I have this which works:</p>
  
  <pre><code>chart.set_title({'name': '=Sheet1!$A$2'})
  </code></pre>
  
  <p>What I want is functionally something like this;</p>
  
  <pre><code>chart.set_title({'name': '=Sheet1!$A$2' + ' to ' + '=Sheet1!$B$2'})
  </code></pre>
  
  <p>This gives an error of <code>Unknown worksheet reference</code>. Both cells contain dates, so it would look something like <code>1/1/2011 to 4/4/2014</code>. I can't find any examples <a href="https://xlsxwriter.readthedocs.org/" rel="nofollow">in the docs</a> of how to do this.</p>
  
  <p>Also tried this based on a now deleted proposed answer:  </p>
  
  <pre><code>chart.set_title({'name': '=CONCATENATE(Sheet1!$A$2, " to ", Sheet1!$B$2)'})
  </code></pre>
  
  <p>It appears, however, that <code>set_title</code> does not accept formulas. It is possible to write this formula into a cell and then refer that cell in the <code>set_title</code>. A bit of a kluge:</p>
  
  <pre><code>worksheet.write(9, 20, '=CONCATENATE(Sheet1!$A$2, " to ", Sheet1!$B$2)')
  chart.set_title({'name': '=Sheet1!$U$10'}) #(9,20)
  </code></pre>