D3.js从数据设置圆半径

Question

我的圈子没有正确地提取他们的半径数据，我觉得我错过了一些明显的东西。

这是我的数据：

var links = [
{source: "Clinton St & Washington Blvd", target: "Dearborn St & Monroe St", trips: 124},
{source: "Clinton St & Washington Blvd", target: "State St & Kinzie St", trips: 132},
{source: "Clinton St & Washington Blvd", target: "Franklin St & Chicago Ave", trips: 136},
{source: "Clinton St & Washington Blvd", target: "Michigan Ave & Washington St", trips: 137},
{source: "Clinton St & Washington Blvd", target: "LaSalle St & Illinois St", trips: 191},
{source: "Clinton St & Washington Blvd", target: "Michigan Ave & Lake St", trips: 231}
];

这是圈子进入的地方：

var circle = svg.append("g").selectAll("circle")
    .data(force.nodes())
  .enter().append("circle")
    .attr("r", function(d) { return d.trips; })
    //.attr("r", 10)
    .call(force.drag);

如果我将“r”静态设置为10，则一切都正确显示。如果我尝试拉半径的“trip”值，我得到1px * 1px。任何提示？

谢谢， 乳木果