列的独特组合

本文介绍了列的独特组合的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

这是我的简化数据集:

foo <- data.frame(var1= c(1:10), var2=rep(1:5,2),var3=rep(1:2,5),var4=rep(3:7,2) )

总共20个变量

foo var1 var2 var3 var4 ... var20 1 1 1 1 3 2 2 2 2 4 3 3 3 1 5 4 4 4 2 6 5 5 5 1 7 6 6 1 2 3 7 7 2 1 4 8 8 3 2 5 9 9 4 1 6 10 10 5 2 7

我需要获得每个周期的3个变量及其总和的唯一组合

I need to get a unique combination of 3 variables and its sum for each period

即.像

var1var2var3 var1var3var4 var1var5var18 etc... 1 6 sum 2 6 3 7 4 10 5 11 6 9 7 10 8 13 9 14 10 17

请注意，var1var3var5与var3var1var5相同

note that var1var3var5 is the same as var3var1var5

推荐答案

按照@Chase的建议，combn为您提供所需的东西:

As @Chase suggested, combn gets you what you want:

nams <- apply( combn(colnames(foo),3), 2, function(z) paste(z, collapse = '')) cols <- combn( ncol(foo), 3) tripleSums <- apply( cols, 2, function(z) rowSums(foo[,z])) colnames(tripleSums) <- nams > tripleSums var1var2var3 var1var2var4 var1var3var4 var2var3var4 [1,] 3 5 5 5 [2,] 6 8 8 8 [3,] 7 11 9 9 [4,] 10 14 12 12 [5,] 11 17 13 13 [6,] 9 10 11 6 [7,] 10 13 12 7 [8,] 13 16 15 10 [9,] 14 19 16 11 [10,] 17 22 19 14