var x = techan.scale.financetime()
        .range([0, width]);
var yVolume = d3.scaleLinear()
        .range([height , height - 60]);

var volume = techan.plot.volume()
        .accessor(candlestick.accessor())
        .xScale(x)
        .yScale(yVolume);
var svg = d3.select("body").append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom)
        .append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

function draw(data) {
  // 新增一個g
  svg.append("g")
            .attr("class", "volume");

  x.domain(data.map(candlestick.accessor().d));
  yVolume.domain(techan.scale.plot.volume(data).domain());
  //在g.volume 根據data 畫出成交量的圖
  svg.select("g.volume").datum(data).call(volume);
}