17.3 Functions with unquoted arguments

Code

library(tidyverse)
df <- tibble(
  a = sample(5), 
  b = sample(5)
)

lag1_mutate <- function(dt, varname, time) { 
  varname_t0 <- paste0(substitute(varname)); 
  varname_t1 <- paste0(substitute(varname), time); 
  dplyr::mutate(dt, !!varname_t1 := lag(!!rlang::sym(varname_t0))) 
}

lag1_mutate(df, a, 2) 
lag1_mutate(df, b, 3)

# A tibble: 5 × 3
      a     b    a2
  <int> <int> <int>
1     1     3    NA
2     5     5     1
3     2     4     5
4     4     2     2
5     3     1     4
# A tibble: 5 × 3
      a     b    b3
  <int> <int> <int>
1     1     3    NA
2     5     5     3
3     2     4     5
4     4     2     4
5     3     1     2

Adapted from here: https://stackoverflow.com/questions/46131829/unquote-the-variable-name-on-the-right-side-of-mutate-function-in-dplyr