LINQ groupby、划分和提取

Question

我的程序正在将获取的相同数据存储在元组列表中

public List<Tuple<int, double, double, double, double>> Temp = new List<Tuple<int, double, double, double, double>>();

以此为例

Temp.Add(new Tuple<int, double, double, double, double>(1, 1.1, 0.4, 0, 100.1));
Temp.Add(new Tuple<int, double, double, double, double>(2, 1.1, 0.4, 1.1, 99.1));
Temp.Add(new Tuple<int, double, double, double, double>(2, 1.1, 0.4, 1.3, 55.1));
Temp.Add(new Tuple<int, double, double, double, double>(1, 2.2, 0.4, 0, 100.2));
Temp.Add(new Tuple<int, double, double, double, double>(2, 2.2, 0.4, 1.1, 50.2));

我必须汇总数据，以便返回具有相同 T2 和 T3 的元组及其 T4 和 T5 除以具有 T2 和 T3 的第一个元组的 T5。

如果我们查看示例，前 3 个元组具有相同的 T2 和 T3，所以我的最终结果将是

[2, 1.1, 0.4, 1.1, (99.1/100.1)] //<- the 2nd tuple with its T5 divided by the 1st tuple T5
[2, 1.1, 0.4, 1.3, (55.1/100.1)] //<- the 3rdtuple with its T5 divided by the 1st tuple T5

那么第4和第5元组也有相同的T2和T3，所以：

[2, 2.2, 0.4, 1.1, (50.2/100.2)] //<- the 5th tuple with its T5 divided by the 4th tuple T5

我被困在：

var norm_result = Temp.GroupBy(x => new { x.Item2, x.Item3 })
    .Select(x => new
    {
        AA = x.Key.Item2,
        BB = x.Key.Item3,
        CC = ??, //Item4
        DD = ??, // Item5 divided by its first value in the group
    });

Answer 1

您的 GroupBy 语句中的每个组都有该组中项目的集合，以及该组的 Key，因此在计算您的常模结果时，您需要枚举每个组以做你的计算。

var norm_result = Temp.GroupBy(x => new{ x.Item2, x.Item3 })
    //Since this select statement returns IEnumerables for each grouping
    //this will be an IEnumerable of IEnumerables. If you want to flatten
    //things into a single IEnumerable you could do a SelectMany here.
    .Select(x =>
    {
        //sort by Item1, hopefully the order of the items after the first
        //doesn't matter since they all seem to be a value of 2.
        var sorted = x.OrderBy(item => item.Item1).ToList();
        //this is the first item in the group that has Item1 == 1
        var first = sorted[0];
        //skip the first since it appears that you are wanting to skip
        //the first value in your norm results and the select here will
        //return an IEnumerable of the remaining items in the group with
        //the dividing logic
        return sorted.Skip(1).Select(item => new
        {
            item.Item1,
            item.Item2,
            item.Item3,
            item.Item4,
            Item5 = item.Item5 / first.Item5
        });
    });

LINQ groupby、划分和提取

LINQ groupby, divide and extract

c#

linq