title: How to draw the triangle symbol?
body: <p>I am trying to implement <a href="http://bl.ocks.org/kiranml1/6972900" rel="nofollow noreferrer">the triangle example</a> yet it fails with d3 v4 for me</p>
  
  <pre><code>triangles = [];
  triangles.push({x : 250});
  triangles.push({x : 350});
  
  var group = svgContainer.append('g').attr('transform','translate('+ xOffset +','+ 30 +')');
  var arc = d3.symbol().type('triangle');
  
  var line = group.selectAll('path')
              .data(triangles)
              .enter()
              .append('path')
              .attr('d',arc)
              .attr('fill','red')
              .attr('stroke','#000')
              .attr('stroke-width',1)
              .attr('transform',function(d){ return "translate("+(d.x)+",0)"; }); 
  </code></pre>
  
  <p>The error:</p>
  
  <blockquote>
    <p>Uncaught TypeError: type.apply(...).draw is not a function</p>
  </blockquote>