Adding column if it does not exist

Question

I have a bunch of data frames with different variables. I want to read them into R and add columns to those that are short of a few variables so that they all have a common

Answer 1

If you had an empty dataframe that contains all the names to check for, you can use bind_rows to add columns.

I used purrr:map_dfr to make the empty tibble with the appropriate column names.

columns = c("top_speed", "mpg") %>%
     map_dfr( ~tibble(!!.x := logical() ) )

# A tibble: 0 x 2
# ... with 2 variables: top_speed , mpg 

bind_rows(columns, mtcars)

# A tibble: 32 x 12
   top_speed   mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
                  
 1        NA  21.0     6 160.0   110  3.90 2.620 16.46     0     1     4     4
 2        NA  21.0     6 160.0   110  3.90 2.875 17.02     0     1     4     4
 3        NA  22.8     4 108.0    93  3.85 2.320 18.61     1     1     4     1