Draw a circle at a point on an NVD3 line chart

问题

how to draw a circle on a peak point in line chart nvd3 e.x:

 nv.addGraph(function() {
  var chart = nv.models.lineChart()
    .useInteractiveGuideline(true)
    ;

  chart.xAxis
    .axisLabel('Time (ms)')
    .tickFormat(d3.format(',r'))
    ;

  chart.yAxis
    .axisLabel('Voltage (v)')
    .tickFormat(d3.format('.02f'))
    ;

  d3.select('#chart svg')
    .datum(data())
    .transition().duration(500)
    .call(chart)
    ;

  nv.utils.windowResize(chart.update);

  return chart;
});

this is an example of line chart and i want to show a circle on average peak points like (10%) is it possible to add circle to the charts after the charts is draw?

• can i add circle to the existing chart in nvd3?
• is it possible to draw another chart on the existing chart to meet this requirement in nvd3?

来源：https://stackoverflow.com/questions/28449394/draw-a-circle-at-a-point-on-an-nvd3-line-chart