Name columns with Dataframe name in a list of Dataframes - r

Question

Objective: Change colname of dataframes in a list of dataframes to the name of each dataframe.
I have some issues when dealing with list and dataframes regarding its name. I have prepared this example to clarify. Hope it is not a mess.
Data:
df1 <- data.frame(A = 1, B = 2, C = 3)
df2 <- data.frame(A = 3, B = 3, C = 2)
dfList <- list(df1,df2)
Output:
> str(dfList)
List of 2
$ :'data.frame': 1 obs. of 3 variables:
..$ A: num 1
..$ B: num 2
..$ C: num 3
$ :'data.frame': 1 obs. of 3 variables:
..$ A: num 3
..$ B: num 3
..$ C: num 2
> names(dfList)
NULL
> names(dfList$df1)
NULL
> names(dfList$df2)
NULL
Manually Input names:
names(dfList) <- c("df1", "df2")
dfList <- lapply(dfList, setNames, c("A", "B", "C"))
Which yields:
> str(dfList)
List of 2
$ df1:'data.frame': 1 obs. of 3 variables:
..$ A: num 1
..$ B: num 2
..$ C: num 3
$ df2:'data.frame': 1 obs. of 3 variables:
..$ A: num 3
..$ B: num 3
..$ C: num 2
> names(dfList)
[1] "df1" "df2"
> names(dfList$df1)
[1] "A" "B" "C"
> names(dfList$df2)
[1] "A" "B" "C"
Desired Solution:
WishedList <- dfList
WishedList[[1]] <- setNames(WishedList[[1]], c("A", "B", "df1"))
WishedList[[2]] <- setNames(WishedList[[2]], c("A", "B", "df2"))
Output solution:
> str(WishedList)
List of 2
$ df1:'data.frame': 1 obs. of 3 variables:
..$ A : num 1
..$ B : num 2
..$ df1: num 3
$ df2:'data.frame': 1 obs. of 3 variables:
..$ A : num 3
..$ B : num 3
..$ df2: num 2
> names(WishedList)
[1] "df1" "df2"
> names(WishedList$df1)
[1] "A" "B" "df1"
> names(WishedList$df2)
[1] "A" "B" "df2"
MyTry:
TryList1 <- lapply(dfList, function(x) setNames(x, c("A", "B", quote(x))))
str(TryList1)
List of 2
$ df1:'data.frame': 1 obs. of 3 variables:
..$ A: num 1
..$ B: num 2
..$ x: num 3
$ df2:'data.frame': 1 obs. of 3 variables:
..$ A: num 3
..$ B: num 3
..$ x: num 2
Doubts:
1) Why when creating the file the names both of the dataframes and of the cols of the dataframes are not included in the list?
2) quote(x) with a single dataframe works. Why not in the list?
> df1 <- data.frame(A = 1, B = 2, C = 3)
> df1 <- setNames(df1, c("A", "B", quote(df1)))
> names(df1)
[1] "A" "B" "df1"
Thank you very much!

Answer 1

Here's a slightly different approach:
df1 <- data.frame(A = 1, B = 2, C = 3)
df2 <- data.frame(A = 3, B = 3, C = 2)
dfList <- list(df1,df2)
names(dfList) <- c("df1", "df2")
Map(function(df, dfn) {names(df)[3] <- dfn; df}, dfList, names(dfList))
#$df1
# A B df1
#1 1 2 3
#
#$df2
# A B df2
#1 3 3 2
You could alternatively use setNames(df, c("A", "B", dfn)) inside the mapply function.
A note on OP's trial: The documentation for quote states:
quote simply returns its argument.
That's why when you use quote(x) inside lapply, it simply returns the character x.

Answer 2

We can lapply() over names(dfList) instead of dfList:
lapply(names(dfList), function(dfn) {
df <- dfList[[dfn]]
names(df)[3] <- dfn
df
})
# [[1]]
# A B df1
# 1 1 2 3
#
# [[2]]
# A B df2
# 1 3 3 2
There's a convenience function in purrr that maps over a list and its names simultaneously:
library(purrr)
imap(dfList, ~ {
names(.x)[3] <- .y
.x
})
# $df1
# A B df1
# 1 1 2 3
#
# $df2
# A B df2
# 1 3 3 2
Or if you're after a short one-liner and don't mind hard-coding "A" and "B":
imap(dfList, ~ setNames(.x, c("A", "B", .y)))
(NB: Essentially those are just variations around Docendo discimus' answer).
Also, not your expected output but maybe of interest for you:
dplyr::bind_rows(dfList, .id = "origin")
# origin A B C
# 1 df1 1 2 3
# 2 df2 3 3 2
Or:
bind_rows(map(dfList, select, -C), .id = "C")
# C A B
# 1 df1 1 2
# 2 df2 3 3