Javascript-交叉过滤器-从服务器获取数据并查找唯一用户

我是JS的新手。我知道以前有人问过这个问题——寻找唯一的用户。我无法工作的是从服务器获取数据的情况。每当我试图从服务器导入数据时，都会出现一个空白屏幕。下面是.js文件：

queue()
.defer(d3.json, "/data2")
.await(makeCharts);

function makeCharts(error, recordsJson) {
//Clean data
var records = recordsJson;
var dateForm = d3.time.format("%Y-%m-%d %H:%M:%S");

records.forEach(function(d) {
    d["timestamp"] = dateForm.parse(d["timestamp"]);
    d["timestamp"].setHours(0,0,0);
});

var ndx = crossfilter(records);
var dateDim = ndx.dimension(function(d) { return d["timestamp"]; }); 

var num_unique_ids_by_date = dateDim.group()
    .reduce(
    function (p, d) {
        if(d.userid in p.userids) p.userids[d.userid] ++;
        else{
            p.userids[d.userid] = 1;
            p.id_count++;
        }
        return p;
    },

    function (p, d) {
        p.userids[d.userid]--;
        if(p.userids[d.userid] === 0){
            delete p.userids[d.userid];
            p.id_count--;
        }
        return p;
    },

    function () {
            return {userids: {},
            id_count: 0};
        });

var timeXChart = dc.rowChart("#time-chartX");        

timeXChart
    .width(650)
    .height(140)
    .dimension(dateDim)
    .group(num_unique_ids_by_date)
    .valueAccessor(function(d){
        return d.value.id_count;
    })
    .elasticX(true) ;      

dc.renderAll();
};

目前我正在关注这个答案-

这是JSON格式的示例数据，位于

localhost:8080/data2

：

[{"userid":81,"timestamp":"2016-07-29 07:01:37"}, 
{"userid":191,"timestamp":"2016-07-31 07:56:05"}, 
{"userid":36,"timestamp":"2016-08-01 01:44:41"},
{"userid":104,"timestamp":"2016-07-28 05:45:51"}, 
{"userid":184,"timestamp":"2016-08-02 06:22:10"},
{"userid":82,"timestamp":"2016-07-28 05:05:10"},
{"userid":220,"timestamp":"2016-08-05 06:39:19"},
{"userid":16,"timestamp":"2016-06-04 03:44:40"},
{"userid":16,"timestamp":"2016-06-04 03:48:29"},
{"userid":16,"timestamp":"2016-06-04 03:48:54"},
{"userid":16,"timestamp":"2016-06-04 03:50:09"},
{"userid":16,"timestamp":"2016-06-04 06:14:34"}];

这是错误日志-

---

错误：属性高度：负值无效。（“-4.269203769230769”）

通常在您的团队出现问题时发生这种情况。您可以组合一个工作示例，或者显示

num\u unique\u ids\u by\u date.all（）

的完整输出是什么样子的？