meteor d3导入数据

Question

我很难将MongoDB中的数据导入D3热图功能。可以在此处找到一个示例：http://bl.ocks.org/tjdecke/5558084 数据如下所示： [对象{_id =＆＃34; DoaB3wnW7CCzxqzug＆＃34;，工作日= 1，小时= 1，值= 12}，对象{_id =＆＃34; RnwxHbRPGdWHBaAYu＆＃34;，工作日= 1，小时= 2，值= 4}]

我的代码如下所示：

Template.weeklyUsageHeatmap.rendered = function() {

    var margin = { top: 20, right: 0, bottom: 100, left: 20 },
          width = 720 - margin.left - margin.right,
          height = 340 - margin.top - margin.bottom,
          gridSize = Math.floor(width / 24),
          legendElementWidth = gridSize*2,
          buckets = 9,

            colors = ["#ffffe5","#fff7bc","#fee391","#fec44f","#fe9929","#ec7014","#cc4c02","#993404","#662506"]
          days = ["Mo", "Tu", "We", "Th", "Fr", "Sa", "Su"],
          times = ["1a", "2a", "3a", "4a", "5a", "6a", "7a", "8a", "9a", "10a", "11a", "12a", "1p", "2p", "3p", "4p", "5p", "6p", "7p", "8p", "9p", "10p", "11p", "12p"];

    var data = WeeklyUsage.find().fetch();

    d3.json(data,
        function(d) {
            return {
                day: +d.weekday, 
                hour: +d.hour,
                value: +d.value
            };
        },
        function(error, data) {
            var colorScale = d3.scale.quantile()
                .domain([0, buckets - 1, d3.max(data, function (d) { return d.value; })])
                .range(colors);

            var svg = d3.select("#chart").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 + ")");

            var dayLabels = svg.selectAll(".dayLabel")
                .data(days)
                .enter().append("text")
                .text(function (d) { return d; })
                .attr("x", 0)
                .attr("y", function (d, i) { return i * gridSize; })
                .style("text-anchor", "end")
                .attr("transform", "translate(-6," + gridSize / 1.5 + ")")
                .attr("class", function (d, i) { return ((i >= 0 && i <= 4) ? "dayLabel mono axis axis-workweek" : "dayLabel mono axis"); });

            var timeLabels = svg.selectAll(".timeLabel")
                .data(times)
                .enter().append("text")
                .text(function(d) { return d; })
                .attr("x", function(d, i) { return i * gridSize; })
                .attr("y", 0)
                .style("text-anchor", "middle")
                .attr("transform", "translate(" + gridSize / 2 + ", -6)")
                .attr("class", function(d, i) { return ((i >= 7 && i <= 16) ? "timeLabel mono axis axis-worktime" : "timeLabel mono axis"); });

            var heatMap = svg.selectAll(".hour")
                .data(data)
                .enter().append("rect")
                .attr("x", function(d) { return (d.hour - 1) * gridSize; })
                .attr("y", function(d) { return (d.weekday - 1) * gridSize; })
                .attr("rx", 4)
                .attr("ry", 4)
                .attr("class", "hour bordered")
                .attr("width", gridSize)
                .attr("height", gridSize)
                .style("fill", colors[0]);

            heatMap.transition().duration(1000)
                .style("fill", function(d) { return colorScale(d.value); });

            heatMap.append("title").text(function(d) { return d.value; });

            var legend = svg.selectAll(".legend")
                .data([0].concat(colorScale.quantiles()), function(d) { return d; })
                .enter().append("g")
                .attr("class", "legend");

            legend.append("rect")
                .attr("x", function(d, i) { return legendElementWidth * i; })
                .attr("y", height)
                .attr("width", legendElementWidth)
                .attr("height", gridSize / 2)
                .style("fill", function(d, i) { return colors[i]; });

            legend.append("text")
                .attr("class", "mono")
                .text(function(d) { return "≥ " + Math.round(d); })
                .attr("x", function(d, i) { return legendElementWidth * i; })
                .attr("y", height + gridSize);
      });

};

我得到的错误是：d为NULL。