title: legend for selected plot objects in MATLAB figure
body: <p>For a MATLAB figure, I have something like:</p>
  
  <pre><code>figure; hold on;
  line ( [1 2], [3 4] );
  line ( [5 6], [7 8] );
  
  plot(x1,y1,'r.');
  plot(x2,y2,'b.');
  </code></pre>
  
  <p>where x1,y1,x2,y2 are all vectors.</p>
  
  <p>How can I add <code>legend</code> for only the last two plots, not for the two lines?</p>