title: Plot multiple variables: label points
body: <p>I have a data.frame with 10-15 entries which looks like this: </p>
  
  <pre><code>      group time1     time2    time3 
  1      F18  4394.500  21043.50 14949.00 
  2      F25  4678.000  23727.65 15683.12 
  3      F30  4909.775  23487.60 16724.40 
  </code></pre>
  
  <p>I plot this with: </p>
  
  <pre><code>plot(variable[,2:4]) 
  </code></pre>
  
  <p>so that a plot with 3 rows and 3 lines for time1, time2 and time3 appears. </p>
  
  <p>Is it somehow possible to label the data points with the values stored in group (F18, F25...)?</p>