Why to quote in dplyr and why not to quote in dplyr?

February 22, 2023

I am teaching an intro to R course and a student asked me a question that I cannot answer.
The question is, why do we not put id and sex in quotes after select in this example

df1 %>%
  select(id, sex)

but we put id in quotes after inner_join in this example

df1 %>%
       inner_join(df2, by = 'id')

The best I could come up with is because it id is after an = sign. But I imagine there is a better answer.

>Solution :

Reference for tidy evaluation: https://dplyr.tidyverse.org/articles/programming.html

Spec for inner_join: https://dplyr.tidyverse.org/reference/mutate-joins.html

Basically, inner_join‘s by = argument takes "A join specification created with join_by(), or a character vector of variables to join by."

# character vector is your provided example
df1 %>%
       inner_join(df2, by = 'id')
# works

# join_by() form uses tidy evaluation
df1 %>%
       inner_join(df2, by = join_by(id))
# also works