How to transform elements in a list to dataframes in R

Question

I have a little problem to solve in R. I have this list a1 in R:

> a1
[[1]]
  x1 x2 x3
1  1  1  1
2  2  2  2
3  2  2  2
4 13 13 13
5 12 12 12
6 23 23 23
7 12 12 12

[[2]]
  x1 x2 x3
1  2  2  2
2  2  2  2
3  2  2  2
4 13 13 13
5 12 12 12
6 23 23 23
7 12 12 12

[[3]]
  x1 x2 x3
1  3  3  3
2  2  2  2
3  2  2  2
4 13 13 13
5 12 12 12
6 23 23 23
7 12 12 12

My problem is I don't get to extract all elements as data frames. For example I used this code for extract them as data frames but I got this error:

for(i in c(1:3))
{
  paste("a",i)=as.data.frame(a1[i])
}
Error in paste("a", i) = as.data.frame(a1[i]) : 
  target of assignment expands to non-language object

My problem is the list has 20 elements and when I put a1=as.data.frame(a1[1]) it works but I would have to write many lines because the for code showed doesn't work. Thanks for your help.

Answer 1

If I understand your goal correctly, two steps:

1. Add names to your list items.
2. Create the objects in your workspace using list2env .

Here's an example:

mylist <- list(data.frame(matrix(1:4, ncol = 2)),
               data.frame(matrix(5:8, ncol = 2)),
               data.frame(matrix(9:12, ncol = 2)))
names(mylist) <- LETTERS[seq_along(mylist)]
mylist
# $A
#   X1 X2
# 1  1  3
# 2  2  4
# 
# $B
#   X1 X2
# 1  5  7
# 2  6  8
# 
# $C
#   X1 X2
# 1  9 11
# 2 10 12

A
# Error: object 'A' not found

list2env(mylist, envir=.GlobalEnv)
# <environment: R_GlobalEnv>

A
#   X1 X2
# 1  1  3
# 2  2  4

Answer 2

You should keep your elements in a list , Better to use lapply to avoid the side effect . Try something like this for example:

 lapply(a1,write.csv)

EDIT add flodel answer:

filenames <- paste0(seq_along(a1), ".csv")
mapply(write.csv, a1, file = filenames)