List< double>的GroupBy宽容行不通 [英] GroupBy of List<double> with tolerance doesn't work

问题描述

我对C#的Groupby有疑问.

我制作了一个List，如下所示:

I made a List like shown below:

List<double> testList = new List<double>();

testList.Add(1);    
testList.Add(2.1);  
testList.Add(2.0);  
testList.Add(3.0);  
testList.Add(3.1);  
testList.Add(3.2);  
testList.Add(4.2);  

我想按以下方式对这些号码列表进行分组:

I'd like to group these number list like this:

group 1 => 1  
group 2 => 2.1 , 2.0  
group 3 => 3.0 , 3.1 , 3.2  
group 4 => 4.2

所以，我写了这样的代码:

so, I wrote code like this:

var testListGroup = testList.GroupBy(ele => ele, new DoubleEqualityComparer(0.5));

DoubleEqualityComparer的定义是这样的:

public class DoubleEqualityComparer : IEqualityComparer<double>
{
    private double tol = 0;

    public DoubleEqualityComparer(double Tol)
    {
        tol = Tol;
    }

    public bool Equals(double d1,double d2)
    {
        return EQ(d1,d2, tol);
    }

    public int GetHashCode(double d)
    {
        return d.GetHashCode();
    }
    public bool EQ(double dbl, double compareDbl, double tolerance)
    {
        return Math.Abs(dbl - compareDbl) < tolerance;
    }
}

但是GroupBy子句不能像下面这样工作:

Yet the GroupBy clause doesn't work like the this:

group 1 => 1  
group 2 => 2.1
group 3 => 2.0  
group 4 => 3.0
group 5 => 3.1
group 6 => 3.2
group 7 => 4.2

我不知道问题是什么.请让我知道是否有问题和解决方案.

I don't know what the problem is. Please let me know if there is problem, and solutions.

推荐答案

使用简单的

use simple Math.Floor to get lower range of the number so that 5.8 should not be treated as 6.

List<double> testList = new List<double>();

testList.Add(1);
testList.Add(2.1);
testList.Add(2.0);
testList.Add(3.0);
testList.Add(3.1);
testList.Add(3.2);
testList.Add(4.2);
testList.Add(5.8);
testList.Add(5.5);

var testListGroup = testList.GroupBy(s => Math.Floor(s)).ToList();

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