CODEWITHSUNDEEP
rdplyr
RRR
RRR

Reputation: 133

Generate a list of tibble from a tibble by using map and select

I want to generate list of tibble from one tibble in the following codes:

tbl = tibble(id=1:10, a = rnorm(10), b = rnorm(10))
tbl_list =  c("a", "b") %>% map(~ tbl %>% select(c("id", .)))

The output I want is:

tbl_list

[[1]]
# A tibble: 2 x 2
     id      a
  <int>  <dbl>
1     1 -0.704
2     2 -0.917

[[2]]
# A tibble: 2 x 2
     id      b
  <int>  <dbl>
1     1 -0.704
2     2 -0.917

However, it shows the error message:

"c("id", .) must evaluate to column positions or names, not a list"

so it seems that . is not recognized a character, but a list

Could you tell me how to avoid this error?

Upvotes: 2

Views: 248

Answers (1)

Ronak Shah
Ronak Shah

Reputation: 388982

You can use .x to access the element

library(tidyverse)
c("a", "b") %>% map(~ tbl %>% select(c("id", .x)))

#[[1]]
# A tibble: 10 x 2
#      id      a
#   <int>  <dbl>
# 1     1  1.42 
# 2     2  1.51 
# 3     3 -0.385
#...

#[[2]]
# A tibble: 10 x 2
#      id      b
#   <int>  <dbl>
# 1     1  1.42 
# 2     2  0.100
# 3     3  1.28 
#....

You can also use . but while using it in chain operation . is referring to the object which is on the left-side of the chain i.e tbl in this case , hence it returns an error. To use . one way is 

c("a", "b") %>% map(~select(tbl, c('id', .)))

Upvotes: 2

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