使用Crossfilter，是否可以在分组时跟踪最大/最小值？ [英] Using Crossfilter, is it possible to track max/min when grouping?

问题描述

使用Crossfilter（https://github.com/square/crossfilter）时，我指定在添加和删除组中的数据时要使用的函数。跟踪运行平均值（使用CoffeeScript）非常简单：

When using Crossfilter (https://github.com/square/crossfilter), I specify functions to use when adding and removing data from a group. It's fairly trivial to keep track of a running average (using CoffeeScript):

reduceAdd = (p, v) ->
  ++p.count;
  p.sum += v.digit;
  p

reduceRemove = (p, v) ->
  --p.count;
  p.sum -= v.digit;
  p

reduceInitial = ->
  {
    count: 0
    sum: 0
    average: ->
      return 0 if this.count == 0
      return this.sum / this.count
  }

是否可以跟踪每组的最大值和最小值？我无法弄清楚如何将所有元素保存在一个巨大的数组中并执行d3.min / d3.max。似乎添加/删除数据的效率非常低。

Is it possible to keep track of the max and min of each group? I can't figure out a way short of keeping all elements in a huge array and doing a d3.min / d3.max. It seems that adding/removing data would be extremely inefficient.

我还想找一种方法告诉Crossfilter从头开始完全重建组，而不是从中删除项目现有的团体。如果应用过滤器，则重置并重建该组。没什么大不了的。

I also looked for a way to tell Crossfilter to completely rebuild the group from scratch, rather than removing items from an existing group. If a filter is applied, the group is reset and rebuilt. Nothing obvious.

推荐答案

在玩了一下之后，你可以通过再次调用group方法来重建组。

After playing around with this for a bit, you can rebuild the group by just calling the group method again.

这篇关于使用Crossfilter，是否可以在分组时跟踪最大/最小值？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！