I have a list of dataframes:
df1 <- data.frame(c(1:5), c(6:10))
df2 <- data.frame(c(1:7))
df3 <- data.frame(c(1:5), c("a", "b", "c", "d", "e"))
my_list <- list(df1, df2, df3)
From my_list, I want to extract the data frames which have only 2 columns (df1 and df3), and put them in a new list.
Maybe you can try lengths
> my_list[lengths(my_list) == 2]
[[1]]
c.1.5. c.6.10.
1 1 6
2 2 7
3 3 8
4 4 9
5 5 10
[[2]]
c.1.5. c..a....b....c....d....e..
1 1 a
2 2 b
3 3 c
4 4 d
5 5 e
It's also possible to subset using lapply and a logical condition (sapply will also work):
my_list[lapply(my_list, ncol) == 2]
[[1]]
c.1.5. c.6.10.
1 1 6
2 2 7
3 3 8
4 4 9
5 5 10
[[2]]
c.1.5. c..a....b....c....d....e..
1 1 a
2 2 b
3 3 c
4 4 d
5 5 e
We could use keep from purrr package with the condition:
library(purrr)
my_list %>% keep(~ ncol(.x) == 2)
[[1]]
c.1.5. c.6.10.
1 1 6
2 2 7
3 3 8
4 4 9
5 5 10
[[2]]
c.1.5. c..a....b....c....d....e..
1 1 a
2 2 b
3 3 c
4 4 d
5 5 e