title: mouseover only on path in d3
body: <p>I have a radar chart with polygons. Now I want them to be filled with color on mouseover, but only when the mouse is on the path. When the mouse is inside the polygon it should have no fill.</p>
  
  <p>So far I tried</p>
  
  <pre><code>svg.selectAll('.polygon')
      .data(scaledData)
      .enter()
      .append('svg:path')
      .attr('d', radialLine)
      .attr('stroke', function(d, i) {return colors(i);})
      .attr('stroke-width', '3')
      .attr('fill', 'none')
      .on("mouseover", function(d) {
        d3.select(this).style("fill", d3.select(this).attr('stroke')).attr('opacity', 0.3);
      })                  
      .on("mouseout", function(d) {
        d3.select(this).style("fill", "none").attr('opacity', 1);
      });
  </code></pre>
  
  <p>Which fills when I'm over the whole polygon. Also I'd like to have the stroke stay the same and not change it's opacity.</p>
  
  <p>Any help is appreciated</p>