tidyverse - prefered way to turn a named vector into a data.frame/tibble

Question

Using the tidyverse a lot i often face the challenge of turning named vectors into a data.frame/tibble with the columns being the names of the vector.
What is the prefered/tidyversey way of doing this?
EDIT: This is related to: this and this github-issue

So i want:

require(tidyverse) vec <- c("a" = 1, "b" = 2) 

to become this:

# A tibble: 1 × 2       a     b   <dbl> <dbl> 1     1     2 

I can do this via e.g.:

vec %>% enframe %>% spread(name, value) vec %>% t %>% as_tibble 

Usecase example:

require(tidyverse) require(rvest) txt <- c('<node a="1" b="2"></node>',          '<node a="1" c="3"></node>')  txt %>% map(read_xml) %>% map(xml_attrs) %>% map_df(~t(.) %>% as_tibble) 

Which gives

# A tibble: 2 × 3       a     b     c   <chr> <chr> <chr> 1     1     2  <NA> 2     1  <NA>     3 

Answer 1

This is now directly supported using bind_rows (introduced in dplyr 0.7.0):

library(tidyverse))  vec <- c("a" = 1, "b" = 2)  bind_rows(vec) #> # A tibble: 1 x 2 #>       a     b #>   <dbl> <dbl> #> 1     1     2 

This quote from https://cran.r-project.org/web/packages/dplyr/news.html explains the change:

bind_rows() and bind_cols() now accept vectors. They are treated as rows by the former and columns by the latter. Rows require inner names like c(col1 = 1, col2 = 2), while columns require outer names: col1 = c(1, 2). Lists are still treated as data frames but can be spliced explicitly with !!!, e.g. bind_rows(!!! x) (#1676).

With this change, it means that the following line in the use case example:

txt %>% map(read_xml) %>% map(xml_attrs) %>% map_df(~t(.) %>% as_tibble)

can be rewritten as

txt %>% map(read_xml) %>% map(xml_attrs) %>% map_df(bind_rows)

which is also equivalent to

txt %>% map(read_xml) %>% map(xml_attrs) %>% { bind_rows(!!! .) }

The equivalence of the different approaches is demonstrated in the following example:

library(tidyverse) library(rvest)  txt <- c('<node a="1" b="2"></node>',          '<node a="1" c="3"></node>')  temp <- txt %>% map(read_xml) %>% map(xml_attrs)  # x, y, and z are identical x <- temp %>% map_df(~t(.) %>% as_tibble) y <- temp %>% map_df(bind_rows) z <- bind_rows(!!! temp)  identical(x, y) #> [1] TRUE identical(y, z) #> [1] TRUE  z #> # A tibble: 2 x 3 #>       a     b     c #>   <chr> <chr> <chr> #> 1     1     2  <NA> #> 2     1  <NA>     3 

Answer 2

The idiomatic way would be to splice the vector with !!! within a tibble() call so the named vector elements become column definitions :

library(tibble) vec <- c("a" = 1, "b" = 2) tibble(!!!vec) #> # A tibble: 1 x 2 #>       a     b #>   <dbl> <dbl> #> 1     1     2 

^{Created on 2019-09-14 by the reprex package (v0.3.0)}