Using rlang::sym inside list definition

Question

I'm writing an R script and I need to allow user to specify the name of variable that will be proccessed by hand, i.e.

var <- 'user_name'

Generally then I refer to that using rlang::sym and quoting/unquoting mechanism. However, I need to use tidyr::replace_na and none of my ideas worked here as the name of the variable has to be specified inside list.

How can I refer to my var in such a case? I was thinking about something like below:

data <- data %>% replace_na(list(sym(var) = 0))

But it didn't work...

Answer 1

We can also put replace_na inside mutate and unquote:

library(dplyr)
library(tidyr)

var <- 'user_name'

data %>%
  mutate(!!var := replace_na(!!sym(var), 0))

Result:

  user_name
1         0
2         1
3         2
4         3
5         4
6         5

Data:

data <- data.frame(user_name = c(NA, 1:5))

Answer 2

Without using any external packages other than dplyr/tidyr, we can change this with setNames

library(dplyr)
library(tidyr)
data %>% 
    replace_na(as.list(setNames(0, var)))
#   user_name
#1         0
#2         3
#3         4

data

data <- data.frame(user_name = c(NA, 3, 4))