title: How to show a tooltip with value when mouseover a svg line graph using d3.js?
body: <p>I'm using D3.js. I want to show a tooltip with corresponding Y-axis value when i mouseover d3.svg.line().</p>
  
  <p>I tried using this code:</p>
  
  <pre><code>d3.svg.line().append("title")
      .text(function(d) { return d; });`
  </code></pre>
  
  <p>but it throws error <strong>has no method 'append'</strong>. Is there any other way?</p>