sum - 在 dc.js 中创建运行总和图

Question

我正在尝试在 crossfilter 中创建运行总和以与 dc.js 一起使用。 我有一组如下记录:

records = [{"date":"2014-01-01","field1":"value1","field2":"value11","value_field":-20},
           {"date":"2014-01-02","field1":"value2","field2":"value12","value_field":100},
           {"date":"2014-01-03","field1":"value1","field2":"value11","value_field":-10},
           {"date":"2014-01-04","field1":"value2","field2":"value12","value_field":150},
           ]

到目前为止，我已经创建了一个 barGraph，它可以很好地与其他维度一起使用，但我希望能够显示理论字段 runnning_total(沿着维度日期)的折线图。

要在 crossfilter 中完成它，我可以使用 fieldx 字段进行分组，并轻松获得相同的运行总图，但使用 dc.js 限制为值的子组。

欢迎任何帮助。

Answer 1

由于您要跨日期分组(根据您的日期维度)，reduce() 函数将用于执行聚合按日期分组，根据下面我的米老鼠示例中突出显示的单元格:

对于运行总计，您需要执行完全不同的操作，向下循环行:

您可以聚合数据，然后附加运行总计字段，如下所示。我还提供了一个示例，说明如何使用 reduce 函数计算平均值:

records = [{ "date": "2014-01-01", "field1": "value1", "field2": "value11", "value_field": -20 },
    { "date": "2014-01-02", "field1": "value2", "field2": "value12", "value_field": 100 },
    { "date": "2014-01-03", "field1": "value1", "field2": "value11", "value_field": -10 },
    { "date": "2014-01-04", "field1": "value2", "field2": "value12", "value_field": 150 }
];


var cf = crossfilter(records);                                 

var dimensionDate = cf.dimension(function (d) {
        return d.date;
    });


function reduceAdd(p, v) {
    p.total += v.value_field;
    p.count++;
    p.average = p.total / p.count;
    return p;
}
function reduceRemove(p, v) {
    p.total -= v.value_field;
    p.count--;
    p.average = p.count ? p.total / p.count : 0;
    return p;
}
function reduceInitial() {
    return {
        total: 0,
        count: 0,
        average: 0,
    };
}



var average = dimensionDate.group().reduce(reduceAdd, reduceRemove, reduceInitial).all();

var averageWithRunningTotal = appendRuningTotal(average);  

function appendRuningTotal(average) {
    var len = average.length,
        runningTotal = 0;
    for (var i = 0; i < len; i++) {
        runningTotal += average[i].value.total;
        average[i].RunningTotal = runningTotal;
    }

    return average;
}

这将返回以下内容:

{"key":"2014-01-01","value":{"total":-20,"count":1,"average":-20},"RunningTotal":-20}
{"key":"2014-01-02","value":{"total":100,"count":1,"average":100},"RunningTotal":80}
{"key":"2014-01-03","value":{"total":-10,"count":1,"average":-10},"RunningTotal":70}
{"key":"2014-01-04","value":{"total":150,"count":1,"average":150},"RunningTotal":220}