title: Plot multiples (time) series in R with legend
body: <p><img src="https://i.stack.imgur.com/ylK6y.png" alt="enter image description here"></p>
  
  <p>According to my datas (cf. picture) called GDP. I would like to know how to plot all the countries in one graph. And I would like to get a legend for each countries like different colours per line or different shape per line. </p>
  
  <p>I know how to plot one series, for instance:</p>
  
  <p>ts.plot(GDP$ALB)</p>
  
  <p>But don't know how to plot all series with a legend.</p>
  
  <p>Thank you</p>