D3.js: draw simple, updatable line graph?

Question

I'm trying to draw a simple line graph in D3, but having a few problems.

I want the graph to be dynamic - so when the data updates, I'd like the graph to transition to the new values. So I need to use D3 transitions somewhere in my code, and I can't find a good example of doing that with a line graph.

以下是我的代码的相关部分.目前,这根本没有任何吸引力.

var data = [
 {
  "air_produced": 0.660985, 
  "air_used": 0.342706, 
  "datestr": "2012-12-01 00:00:00", 
  "energy_used": 0.106402
 } ... ];
var parseDate = d3.time.format("%Y-%m-%d %H:%M:%S");
data.forEach(function(d) {
  d.date = parseDate.parse(d.datestr);
});

var x = d3.time.scale().range([0, width]);
var y = d3.scale.linear().range([height, 0]);

var line = d3.svg.line()
  .x(function(d) { return x(d.date); })
  .y(function(d) { return y(d.energy_used); });

// How to draw the line?
var linegraph = d3.select("path.line").datum(data);
line.transition().duration(1000).attr("d", line);
linegraph.enter().append("path")
    .attr("class", "line")
    .attr("d", line);

JSFiddle这里有完整的图表:http://jsfiddle.net/zNX8p/

Answer 1

明白了（我想）：

var linegraph = svg.selectAll("path.line").data([data], function(d) { return d.date; });

linegraph.transition().duration(1000).attr('d', line);

linegraph.enter().append("path")
    .attr("class", "line")
    .attr("d", line);

datum不返回enter选择，因此您需要通过传递数据data。