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 already have a dataframe with all the required columns, say

library(tidyverse)  

df_with_required_columns = 
      mtcars %>% 
      mutate(top_speed = NA_real_) %>%
      select(top_speed, mpg)

then you can simply bind_rows filtering out all the rows:

mtcars %>%
  rownames_to_column("car") %>%
  bind_rows( df_with_required_columns %>% filter(F) ) %>%
  select(car, top_speed, mpg, everything())

Note that missing columns will take the type from df_with_required_columns.