title: Time series multiple plot for different group in R
body: <p>I have a large data frame of several variables (around 50)  with first column as <code>date</code> and second column <code>id</code>. </p>
  
  <p>My data roughly look like this:</p>
  
  <pre><code>df &lt;- data.frame(date = c("01-04-2001 00:00","01-04-2001 00:00","01-04-2001 00:00",
                        "01-05-2001 00:00","01-05-2001 00:00","01-05-2001 00:00",
                        "01-06-2001 00:00","01-06-2001 00:00","01-06-2001 00:00",
                        "01-07-2001 00:00","01-07-2001 00:00","01-07-2001 00:00"), 
               id = c(1,2,3,1,2,3,1,2,3,1,2,3), a = c(1,2,3,4,5,6,7,8,9,10,11,12), 
               b = c(2,2.5,3,3.2,4,4.6,5,5.6,8,8.9,10,10.6))
  </code></pre>
  
  <p>I want time series plots for all three ids separately in same graph of variables, <code>a</code> and <code>b</code> in different graphs.</p>
  
  <p>I tried <code>ggplot</code>  but it didn't work. Please help me</p>