Using quoted variable names when creating functions containing ellipses (i.e. '…') in dplyr

I am trying to learn how to use the ellipses (...) when I program using dplyr. I cannot work out how to pass a character into the ellipses. Here is a toy problem to illustrate

data.frame(var1 = factor(sample(x = letters[1:3],
                                size = 10,
                                replace = T))) -> df

Now say I want to get simple frequencies of each level of the factor. I make a simple function to do that

levelFunct <- function(.data, ...) {
  .data %>%
    group_by(...) %>%
      summarise(count = n()) %>%
        mutate(tot = sum(count),
               perc = round(count/tot*100,2))

Now when I run the function this way, just passing the name of the variable into the ellipse argument without quotation marks

levelFunct(df, var1)

I get the following output

  var1  count   tot  perc
  <fct> <int> <int> <dbl>
1 a         1    10    10
2 b         2    10    20
3 c         7    10    70

So far so good. But if I pass the function into the ellipse argument with quotation marks

levelFunct(df, "var1")

I get the following output

  `"var1"` count   tot  perc
  <chr>    <int> <int> <dbl>
1 var1        10    10   100

So how do I replicate the result from the first run using a quoted variable name?

I tried enclosing the ellipse in the group_by function in double brackets ([[...]]) but just got an error.

>Solution :

In those situations, you must use the .data pronoun:

levelFunct(df, .data[["var1"]])


You can pass more parameters aside that, literal string or var name.

levelFunct(df, .data[["var1"]], var2, .....)

in general, methods described here are valid:

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