R：针对特定子集按行分组和求和

Olga 发表于 Dev

奥尔加

我无法解决以下问题，因此需要您的帮助：

初始点：

x1<-matrix(c("A","A","A","A","A","B","B","B","B","B",
"x1","x2","x3","x4","x5","x1","x2","x3","x4","x5",
1,2,3,4,5,6,7,8,9,10),nrow = 10, ncol = 3)
x1

所需结果：

x2<- matrix(c("A","A","B","B",6,9,21,19),nrow = 4, ncol = 2)
x2

对于A：x1 + x1 + x3 = 1 + 2 + 3 = 6，x4 + x5 = 4 + 5 = 9
对于B：x1 + x2 + x3 = 6 + 7 + 8 = 21，x4 + x5 = 9 + 10 = 19

我想避免生成两个单独的数据集（一个用于x1，x2，x3，另一个用于x4，x5）。有谁知道如何解决这个问题？非常感谢！

冰激凌巨嘴鸟

data.table

library(data.table)
as.data.table(x1)[, .(vsum = sum(as.numeric(V3))), .(V1, grepl('[1-3]', V2))]
#    V1 grepl vsum
# 1:  A  TRUE    6
# 2:  A FALSE    9
# 3:  B  TRUE   21
# 4:  B FALSE   19

基数R：

aggregate(as.numeric(x1[,3]), by = list(!grepl('[1-3]', x1[, 2]), x1[, 1]), sum)[, -1]
#   Group.2  x
# 1       A  6
# 2       A  9
# 3       B 21
# 4       B 19

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