扩展列表以在组中包括所有可能的成对组合 [英] Expanding a list to include all possible pairwise combinations within a group

问题描述

我目前正在进行随机化处理，其中将给定人群的个体采样并放入定义大小的组中.结果是一个数据帧，如下所示:

I am currently running a randomization where individuals of a given population are sampled and placed into groups of defined size. The result is a data frame seen below:

Ind Group
Sally   1
Bob 1
Sue 1
Joe 2
Jeff    2
Jess    2
Mary    2
Jim 3
James   3

有没有能让我扩展数据集以显示组配对中所有可能的功能?(下面的所需输出).配对不需要是互惠的.

Is there a function which will allow me to expand the data set to show every possible within group pairing? (Desired output below). The pairings do not need to be reciprocal.

Group   Ind1    Ind2
1   Sally   Bob
1   Sally   Sue
1   Sue Bob
2   Joe Jeff
2   Joe Jess
2   Joe Mary
2   Jeff    Jess
2   Jess    Mary
2   Jeff    Mary
3   Jim James

我觉得必须在dplyr中做到这一点，但对于我的一生，我似乎无法解决它.

I feel like there must be a way to do this in dplyr, but for the life of me I can't seem to sort it out.

推荐答案

以下是使用 data.table 的选项.转换为 data.table ( setDT(dt))，进行按"Group"分组的交叉联接( CJ )，并删除重复的元素

Here is an option using data.table. Convert to data.table (setDT(dt)), Do a cross join (CJ) grouped by 'Group' and remove the duplicated elements

library(data.table)
setDT(dt)[, CJ(Ind1 = Ind, Ind2 = Ind, unique = TRUE)[Ind1 != Ind2], 
             Group][!duplicated(data.table(pmax(Ind1, Ind2), pmin(Ind1, Ind2)))]
#   Group  Ind1  Ind2
#1:     1   Bob Sally
#2:     1   Bob   Sue
#3:     1 Sally   Sue
#4:     2  Jeff  Jess
#5:     2  Jeff   Joe
#6:     2  Jeff  Mary
#7:     2  Jess   Joe
#8:     2  Jess  Mary
#9:     2   Joe  Mary
#10:    3 James   Jim

---

或按组"使用 combn

setDT(dt)[, {temp <- combn(Ind, 2); .(Ind1 = temp[1,], Ind2 = temp[2,])}, Group]

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