Rlang

Tidy dots features

my_cases <-   rlang::quos(
    Species == "setosa" ~ "S", 
    TRUE ~ "other"
    )

out <-  tiris %>% 
            mutate(new_lable = case_when(!!! my_cases))

curly-curly(): abstracts quote-and-unquote into a single interpolation step

quote and unquote version

max_by <- function(data, var, by) {
  data %>%
    group_by(!!enquo(by)) %>%
    summarise(maximum = max(!!enquo(var), na.rm = TRUE))
}

starwars %>% max_by(mass, by = gender)

curly-curly version

max_by <- function(data, var, by) {
  data %>%
    group_by({{ by }}) %>%
    summarise(maximum = max({{ var }}, na.rm = TRUE))
}

starwars %>% max_by(var = height, by = gender)

env(): Create a new environment

e1 <- rlang::env(a = 1, b = 2, c = 3)
e1$a

put a list into an environment

objs <- list(b = "foo", c = "bar")
env <- env(a = 1, !!! objs)
env$c

assign values with the definition operator :=

var <- "a"
env <- env(!!var := "A")
env$a

exec(): Execute functions

exec("mean", x = 1:10, na.rm = TRUE, trim = 0.1)

Using dots features

args <- list(x = 1:10, na.rm = TRUE, trim = 0.1)
exec("mean", !!!args)

r title = 'assign values with the definition operator :=' arg_name <- "na.rm" arg_val <- TRUE exec("mean", 1:10, !!arg_name := arg_val)