title: Matlab Plot XTickLabel valid strings
body: <p>I have a plot:</p>
  
  <pre><code>x = [0 1 2 3];
  y = [0 0 1 1];
  
  plot (x, y, 'k');
  </code></pre>
  
  <p>I want to use labels at X-axis, and it works:</p>
  
  <pre><code>set(gca,'XTick',[0:3]) % This automatically sets 
  labels = ['0'; 'T'; 'T'; '1';];
  set(gca,'XTickLabel',labels)
  </code></pre>
  
  <p>However, when I change <code>T</code> to <code>T0</code>. It doesn't work.</p>
  
  <p><strong>Q1:</strong> What are the valid strings of <code>XTickLabel</code>? </p>
  
  <p><strong>Q2:</strong> How can I use strings like T0, T1. Or is that possible to use characters with subindex like $A_2$ in latex format. </p>