r - 如何从数据框列表中附加列？

Question

假设我有以下数据框列表:

lst <- list(
a=data.frame(key=c(1,2,3), val=c(10,20,30)), 
b=data.frame(key=c(1,2,3), val=c(100,200,300)), 
c=data.frame(key=c(1,2,3), val=c(1000,2000,3000)), 
d=data.frame(key=c(1,2), val=c(10000,20000)))

我如何创建一个 data.frame 如下？ (或类似):

  key val.a val.b val.c val.d
1   1    10   100  1000 10000
2   2    20   200  2000 20000
3   3    30   300  3000 NA

我试图这样做(但失败):

Browse[2]> Reduce(function(x,y) merge(x, y, by = 'key', all.x = T), lst)
  key val.x val.y val.x val.y
1   1    10   100  1000 10000
2   2    20   200  2000 20000
3   3    30   300  3000 NA
Warning message:
In merge.data.frame(x, y, by = "key", all.x = T) :
  column names ‘val.x’, ‘val.y’ are duplicated in the result

NOTE: I would prefer a base-R solution but am interested in other ways of doing this

Answer 1

我们可以使用 inner_join与 reduce之后 renaming第二列与相应的 list姓名

library(purrr)
library(dplyr)
library(stringr)
imap(lst, ~ { nm <- .y
              .x %>% 
                rename_at(vars(val), ~ str_c(., ".", nm))}) %>% 
    reduce(full_join, by = 'key')
#    key val.a val.b val.c val.d
#1   1    10   100  1000 10000
#2   2    20   200  2000 20000
#3   3    30   300  3000 30000

或在 base R ，我们使用 Map对列进行重命名，然后在 OP 的帖子中，执行 merge内Reduce

Reduce(function(...) merge(..., by = 'key', all = TRUE), 
       Map(function(x, y) setNames(x, c('key',
           paste0(names(x)[-1], ".", y))), lst, names(lst)))
#  key val.a val.b val.c val.d
#1   1    10   100  1000 10000
#2   2    20   200  2000 20000
#3   3    30   300  3000 30000