如何在D3龙卷风图表中将Y轴居中

var svg = d3.select("body")
  .append("svg")
  .attr("width", width)
  .attr("height", height);

var margin = { top: 20, right: 20, bottom: 30, left: 40 };
var width = 500 - margin.left - margin.right;
var height = 400 - margin.top - margin.bottom;

var data = [10, 20, 30, 40, 50];
var yScale = d3.scaleLinear()
  .domain([0, d3.max(data)])
  .range([height, 0]);

var yAxis = d3.axisLeft(yScale);
svg.append("g")
  .attr("class", "y-axis")
  .call(yAxis);

svg.select(".y-axis")
  .attr("transform", "translate(" + margin.left + "," + (margin.top + height/2) + ")");