Crossfilter平均组

我试图计算总和（查询时间）的平均查询时间，然后将它们除以一个计数。我怎样才能得到计数？

var querytimeByMonthGroup = moveMonths.group().reduceSum(function (d) {
    return d.querytime;
});

var querytimeByMonthGroup = moveMonths.group().reduceSum(function (d) {
    return d.querytime / d.count; ???
});

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我对crossfilter不熟悉，只是刚开始玩。 可能有更好的方法，但是这提供了一种方法来计算用于分组的维数（我不是100％清楚地知道d.count指的是用于分组的维数，使用如果需要另一个分组）。

示例源自以下代码：https：//github.com/square/crossfilter/wiki/API-Reference

var payments = crossfilter([
    {date: "2011-11-14T16:17:54Z", quantity: 2, total: 190, tip: 100, type: "tab"},
    {date: "2011-11-14T16:20:19Z", quantity: 2, total: 190, tip: 100, type: "tab"},
    {date: "2011-11-14T16:28:54Z", quantity: 1, total: 300, tip: 200, type: "visa"},
    {date: "2011-11-14T16:30:43Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T16:48:46Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T16:53:41Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T16:54:06Z", quantity: 1, total: 100, tip: 0, type: "cash"},
    {date: "2011-11-14T16:58:03Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T17:07:21Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T17:22:59Z", quantity: 2, total: 90, tip: 0, type: "tab"},
    {date: "2011-11-14T17:25:45Z", quantity: 2, total: 200, tip: 0, type: "cash"},
    {date: "2011-11-14T17:29:52Z", quantity: 1, total: 200, tip: 100, type: "visa"}
]);

var paymentsByType = payments.dimension(function(d) { return d.type; }),
        paymentVolumeByType = paymentsByType.group(),
        counts = paymentVolumeByType.reduceCount().all(),
        countByType = {}; 

// what is returned by all is a pseudo-array. An object that behaves like an array. 
// Trick to make it a proper array
Array.prototype.slice.call(counts).forEach(function(d) { countByType[d.key] = d.value; })
var paymentVolumeByType = paymentVolumeByType.reduceSum(function(d, i) { 
    console.log(d.total, d.type, countByType[d.type])
    return d.total / countByType[d.type]; 
});
// accessing parentVolumeByType to cause the reduceSum function to be called
var topTypes = paymentVolumeByType.top(1);

---

我认为一个更好的（以及预期的）做法是通过定义你自己的reduce函数（add，remove，initial）。 然后，您可以将运行总和，计数等存储在减少功能中，并在筛选器从组中删除数据时适当调整它们。

在这个类似的问题中给出了使用平均值和最小值和最大值的示例：使用Crossfilter，分组时是否可以跟踪最大值/最小值？

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