multiline chart using nvd3's preferred json structure

a_chart.js

var chart = d3.select("#chart").append("svg")
    .attr("width", w)
    .attr("height", h)
    .append("g")
    .attr("id", "plotarea")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")")

    // DRAW DATALINES
    path = chart.selectAll("path.dataline")
        .data(data)
    path.enter().append("path")
        .attr("id", function (d) { return d.key; })
        .attr("class", function (d) { return d.key.replace("-", " ")+" dataline"; })
        .style("stroke-width", 2)
        .style("stroke", "black")
        .style("fill", "none")
        .style("stroke-opacity", 0)
        .transition()
        .duration(1500)
        .delay(1500)
        .style("stroke-opacity", .1)
        .attr('d', function (d) { return line(d.values)});



    // DRAW DATAPOINTS
    var group = chart.selectAll("g.datapoint") // need a svg:g for the outer loop
        .data(data)
    var g = group.enter().append("g")
        .attr("class", function (d) { return d.key.replace("-", " ") + " datapoint"; })
        .selectAll('circle')
        .data(function (d) { return d.values; })
    var circle = g.enter().append("circle")
        .attr("cx", function(d) { return x(d[0]); })
        .attr("cy", function(d) { return y(d[1]); })
        .attr("r", 3)
        // .attr("stroke-opacity", 0)
        .attr("fill-opacity", 0)
        .on("mouseover", mouseover)
        .on("mouseout", mouseout)
        .on("click", selectpoint);

    group.exit().remove()

data.json

data = [
    {
        "key":"brw-a",
        "values":[
            ["2012-07-05T00:00:00", 0.0 ],
            ["2012-07-06T23:59:59", 1.0 ],
            ["2012-07-07T06:31:47", 0.0 ],
            ["2012-07-08T23:59:59", 3.0 ]
        ]
    },
    {
        "key":"brw-c",
        "values":[
            ["2012-07-11T00:00:00", 0.0 ],
            ["2012-07-07T00:00:00", 2.0 ],
            ["2012-07-05T23:59:59", 4.0 ]
        ]
    },
    {
        "key" : "yfb-b",
        "values" : [
            [ "2012-07-11T00:00:00", 10.0 ],
            [ "2012-07-11T02:33:56", 8.0 ],
            [ "2012-07-11T02:55:58", 6.0 ],
            [ "2012-07-11T10:58:04", 4.0 ],
            [ "2012-07-11T11:16:48", 0.0 ],
            [ "2012-07-11T14:36:35", 4.0 ],
            [ "2012-07-11T15:08:25", 6.0 ],
            [ "2012-07-11T15:12:15", 8.0 ],
            [ "2012-07-11T15:26:40", 10.0 ],
            [ "2012-07-11T23:59:59", 10.0 ],
            [ "2012-07-10T12:53:56", 2.0 ],
            [ "2012-07-10T12:55:41", 4.0 ],
            [ "2012-07-10T12:59:12", 6.0 ],
            [ "2012-07-10T13:01:59", 8.0 ],
            [ "2012-07-10T14:15:49", 10.0 ],
            [ "2012-07-10T23:59:59", 10.0 ],
            [ "2012-07-09T00:00:00", 6.0 ],
            [ "2012-07-09T08:29:41", 2.0 ],
            [ "2012-07-08T12:03:59", 0.0 ],
            [ "2012-07-08T14:28:47", 2.0 ],
            [ "2012-07-08T15:19:16", 4.0 ],
            [ "2012-07-05T20:47:41", 0.0 ],
            [ "2012-07-05T23:59:59", 0.0 ]
      ]
  },
  {
        "key" : "zau-b",
        "values" : [
            [ "2012-07-10T00:31:25", 10.0 ],
            [ "2012-07-10T00:31:26", 6.0 ],
            [ "2012-07-10T00:31:27", 0.0 ],
            [ "2012-07-10T01:08:33", 4.0 ],
            [ "2012-07-10T01:47:55", 6.0 ],
            [ "2012-07-10T01:51:17", 12.0 ],
            [ "2012-07-10T02:41:40", 14.0 ],
            [ "2012-07-10T09:38:11", 10.0 ],
            [ "2012-07-10T14:46:26", 12.0 ],
            [ "2012-07-10T14:46:28", 14.0 ],
            [ "2012-07-10T14:50:17", 16.0 ],
            [ "2012-07-10T22:05:23", 14.0 ],
            [ "2012-07-10T23:59:59", 14.0 ],
            [ "2012-07-09T14:59:29", 6.0 ],
            [ "2012-07-09T16:10:27", 2.0 ],
            [ "2012-07-09T23:59:59", 2.0 ],
            [ "2012-07-08T00:00:00", 0.0 ],
            [ "2012-07-08T14:55:30", 2.0 ],
            [ "2012-07-08T14:58:35", 4.0 ],
            [ "2012-07-08T15:02:43", 6.0 ],
            [ "2012-07-08T23:59:59", 6.0 ],
            [ "2012-07-07T00:00:00", 0.0 ],
            [ "2012-07-07T02:55:25", 2.0 ],
            [ "2012-07-07T03:00:25", 4.0 ],
            [ "2012-07-07T06:07:55", 6.0 ],
            [ "2012-07-07T06:12:00", 8.0 ],
            [ "2012-07-07T09:52:22", 6.0 ],
            [ "2012-07-07T23:59:59", 6.0 ],
            [ "2012-07-06T00:00:00", 10.0 ],
            [ "2012-07-06T08:14:45", 8.0 ],
            [ "2012-07-06T08:38:38", 6.0 ],
            [ "2012-07-06T09:56:11", 4.0 ],
            [ "2012-07-06T15:10:44", 6.0 ],
            [ "2012-07-06T22:20:08", 2.0 ],
            [ "2012-07-06T22:20:09", 0.0 ],
            [ "2012-07-06T23:59:59", 0.0 ],
            [ "2012-07-05T00:00:00", 0.0 ],
            [ "2012-07-05T15:15:43", 2.0 ],
            [ "2012-07-05T15:15:44", 4.0 ],
            [ "2012-07-05T23:59:59", 4.0 ]
      ]
  }
]