Question

I do know about the basics of combining a list of data frames into one as has been answered before. However, I am interested in smart ways to maintain row names. Suppose I have a list of data frames that are fairly equal and I keep them in a named list.

library(plyr)
library(dplyr)
library(data.table)

a = data.frame(x=1:3, row.names = letters[1:3])
b = data.frame(x=4:6, row.names = letters[4:6])
c = data.frame(x=7:9, row.names = letters[7:9])

l = list(A=a, B=b, C=c)

When I use do.call, the list names are combined with the row names:

> rownames(do.call("rbind", l))
[1] "A.a" "A.b" "A.c" "B.d" "B.e" "B.f" "C.g" "C.h" "C.i"

When I use any of rbind.fill, bind_rows or rbindlist the row names are replaced by a numeric range:

> rownames(rbind.fill(l))
> rownames(bind_rows(l))
> rownames(rbindlist(l))
[1] "1" "2" "3" "4" "5" "6" "7" "8" "9"

When I remove the names from the list, do.call produces the desired output:

> names(l) = NULL
> rownames(do.call("rbind", l))
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i"

So is there a function that I'm missing that provides some finer control over the row names? I do need the names for a different context so removing them is sub-optimal.

Answer 1

To preserve rownames, you can simply do:

do.call(rbind, unname(l))

#  x
#a 1
#b 2
#c 3
#d 4
#e 5
#f 6
#g 7
#h 8
#i 9

Or as you underlined by setting the rownames of l to NULL , this can be also done by:

do.call(rbind, setNames(l, NULL))

Answer 2

我们可以在绑定之前使用 dplyr 包中的 add_rownames ：

rbind_all(lapply(l, add_rownames))

# Source: local data frame [9 x 2]
#
#   rowname x
# 1       a 1
# 2       b 2
# 3       c 3
# 4       d 4
# 5       e 5
# 6       f 6
# 7       g 7
# 8       h 8
# 9       i 9

Answer 3

Why not only using rbind:

 rbind(l$A, l$B, l$C)

Combine a list of data frames into one preserving row names

3 个答案: