title: Plot certain columns of a data frame
body: <p>My data frame has the following structure named dat:</p>
  
  <pre><code>  No.  Action  Title          Replies  PlusOnes  Reshares  Url                    
     1    Share   SomeTitle     2        3         1         http://plus.google.com 
     2    Post    AnotherTitle  3        4         5         http://plus.google.com
  </code></pre>
  
  <p>Here is the <code>dput(dat)</code> of my data:</p>
  
  <pre><code>structure(list(No. = 1:2, Action = c("Share", "Post"), Title = c("Some Title", 
  "Another Title"), Replies = 2:3, PlusOnes = 3:4, Reshares = c(1L, 
  5L), Url = c("http://plus.google.com", "http://plus.google.com"
  )), .Names = c("No.", "Action", "Title", "Replies", "PlusOnes", 
  "Reshares", "Url"), class = "data.frame", row.names = c(NA, -2L
  ))
  </code></pre>
  
  <p>How can I plot the columns <code>Replies</code>, <code>PlusOnes</code> and <code>Reshares</code> in a graph?
  The x axis should be the <code>No.</code>, the y axis the number of Replies/PlusOnes/Reshares, and these columns should each have a separate line in the graph.</p>
  
  <p>Regards</p>