tidyr::separate dynamically creating new column names

[howardbaek]

Say I have a csv file containing this sort of data from the tidyr documentation:

df <- data.frame(x = c("a.b", "a.d", "b.c"))
df %>% separate(x, c("A", "B"))

  A B
1 a b
2 a d
3 b c

This works great if you know how many columns will be in your output. In my case, I'm connecting this dataset to a shinydashboard that dynamically generates a plot based on this data.

I'd like to separate the column x into different columns by a separator . and dynamically generate custom column names along the way. Something I had in mind:

df %>% separate(col = x, 
                into = paste0("x_", 1:2))
  x_1 x_2
1   a   b
2   a   d
3   b   c

but I'd like the numbers coming after _ to be reactively generated depending on the number of columns x is separated into.

[technocrat]

suppressPackageStartupMessages({
  library(tidyr)
  library(stringr)
})

begin <- letters
finish <- rev(letters)
var <- paste0(begin,".",finish)  
df_ <- data.frame(x = var)
out_length <- length(str_split(df_[1,1],"\\.")[[1]])

df_ %>% separate(col = x, 
             into = paste0("x_", 1:out_length))
#>    x_1 x_2
#> 1    a   z
#> 2    b   y
#> 3    c   x
#> 4    d   w
#> 5    e   v
#> 6    f   u
#> 7    g   t
#> 8    h   s
#> 9    i   r
#> 10   j   q
#> 11   k   p
#> 12   l   o
#> 13   m   n
#> 14   n   m
#> 15   o   l
#> 16   p   k
#> 17   q   j
#> 18   r   i
#> 19   s   h
#> 20   t   g
#> 21   u   f
#> 22   v   e
#> 23   w   d
#> 24   x   c
#> 25   y   b
#> 26   z   a

^{Created on 2020-10-27 by the reprex package (v0.3.0.9001)}