Initialize an empty tibble with column names and 0 rows

Question

I have a vector of column names called tbl_colnames.

I would like to create a tibble with 0 rows and length(tbl_colnames) columns.

The best way I've found of doing this is...

tbl <- as_tibble(data.frame(matrix(nrow=0,ncol=length(tbl_colnames)))

and then I want to name the columns so...

colnames(tbl) <- tbl_colnames.

My question: Is there a more elegant way of doing this?

something like tbl <- tibble(colnames=tbl_colnames)

Solution 1

Since you want to combine a list of tibbles. You can just assign NULL to the variable and then bind_rows with other tibbles.

res = NULL
for(i in tibbleList)
   res = bind_rows(res,i)

However, a much efficient way to do this is

bind_rows(tibbleList) # combine all tibbles in the list

Solution 2

my_tibble <- tibble(
  var_name_1 = numeric(),
  var_name_2 = numeric(),
  var_name_3 = numeric(),
  var_name_4 = numeric(),
  var_name_5 = numeric()
)

Haven't tried, but I guess it works too if instead of initiating numeric vectors of length 0 you do it with other classes (for example, character()).

This SO question explains how to do it with other R libraries.

According to this tidyverse issue, this won't be a feature for tribbles.

Solution 3

For anyone still interested in an elegant way to create a 0-row tibble with column names given by a character vector tbl_colnames:

tbl_colnames %>% purrr::map_dfc(setNames, object = list(logical()))

or:

tbl_colnames %>% purrr::map_dfc(~tibble::tibble(!!.x := logical()))

or:

tbl_colnames %>% rlang::rep_named(list(logical())) %>% tibble::as_tibble()

This, of course, results in each column being of type logical.

Solution 4

You could abuse readr::read_csv, which allow to read from string. You can control names and types, e.g.:

tbl_colnames <- c("one", "two", "three", "c4", "c5", "last")
read_csv("\n", col_names = tbl_colnames) # all character type
read_csv("\n", col_names = tbl_colnames, col_types = "lcniDT") # various types

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Comments

[colorlace]

Thank you for your answer. It was a list of lists (not a list of tibbles), but this seems to work anyway!

[colorlace]

Thanks. I was hoping to use the tbl_colnames vector directly when I asked this question, but it's true that this is one way to do it (if a bit cumbersome). In any case, it could be helpful for others seeking different ways to init tibbles.

[Aren Cambre]

This answer is responsive to a comment that is only peripherally related the title of and question posted on this page.