Question

我发现了许多类似的问题，但没有一个适合我的问题。我有两个大型数据框，很少有公共列。我正在尝试通过引用将第一个df的值分配给第二个df。

我尝试了更多组合，但是没人能正常工作，例如：

library(data.table)

#create dfs
set.seed(32)
DB <- data.frame(A=sample(c("A","B","C","D","E"),30,replace = T))
DB2 <- data.frame(A=sample(c("A","B","C","D","E","F","G"),60,replace = T),
                              B=rep(rnorm(60,mean=5)),
                              C=rep(rnorm(60,mean=10)))
#loop 
for (i in c("B","C")){
setDT(DB)[DB2,  i := i, on = .(A == A)]}

因此，我想循环以下代码：

setDT(DB)[DB2, B := B, on = .(A == A)]
setDT(DB)[DB2, C := C, on = .(A == A)]
> DB
    A        B         C
 1: C 5.593191 10.697466
 2: C 5.593191 10.697466
 3: E 4.482933  8.726371
 4: D 5.454512 11.054162
 5: A 4.306571 11.427917
 6: E 4.482933  8.726371
 7: D 5.454512 11.054162
 8: E 4.482933  8.726371
 9: D 5.454512 11.054162
10: B 4.741633 10.846106
11: D 5.454512 11.054162
12: B 4.741633 10.846106
13: D 5.454512 11.054162
14: D 5.454512 11.054162
15: B 4.741633 10.846106
16: D 5.454512 11.054162
17: D 5.454512 11.054162
18: C 5.593191 10.697466
19: D 5.454512 11.054162
20: E 4.482933  8.726371
21: D 5.454512 11.054162
22: E 4.482933  8.726371
23: C 5.593191 10.697466
24: A 4.306571 11.427917
25: C 5.593191 10.697466
26: E 4.482933  8.726371
27: C 5.593191 10.697466
28: C 5.593191 10.697466
29: C 5.593191 10.697466
30: D 5.454512 11.054162
    A        B         C

任何帮助将不胜感激

Answer 1

尝试：

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更新

弗朗克（Franck）的建议应该也可以很好地工作，并且对于大量列而言更有效（请注意library(data.table) #create dfs set.seed(32) DB <- data.frame(A=sample(c("A","B","C","D","E"),30,replace = T)) DB2 <- data.frame(A=sample(c("A","B","C","D","E","F","G"),60,replace = T), B=rep(rnorm(60,mean=5)), C=rep(rnorm(60,mean=10))) #try setDT(DB)[DB2, c("B", "C") := list(B, C), on = .(A == A)] DB #output A B C 1: C 5.593191 10.697466 2: C 5.593191 10.697466 3: E 4.482933 8.726371 4: D 5.454512 11.054162 5: A 4.306571 11.427917 6: E 4.482933 8.726371 7: D 5.454512 11.054162 8: E 4.482933 8.726371 9: D 5.454512 11.054162 10: B 4.741633 10.846106 11: D 5.454512 11.054162 12: B 4.741633 10.846106 13: D 5.454512 11.054162 14: D 5.454512 11.054162 15: B 4.741633 10.846106 16: D 5.454512 11.054162 17: D 5.454512 11.054162 18: C 5.593191 10.697466 19: D 5.454512 11.054162 20: E 4.482933 8.726371 21: D 5.454512 11.054162 22: E 4.482933 8.726371 23: C 5.593191 10.697466 24: A 4.306571 11.427917 25: C 5.593191 10.697466 26: E 4.482933 8.726371 27: C 5.593191 10.697466 28: C 5.593191 10.697466 29: C 5.593191 10.697466 30: D 5.454512 11.054162 A B C返回一个命名列表）

mget

通过列循环引用分配

1 个答案: