Selecting Syntax

Selectors

The cards package also utilizes selectors: selectors from the tidyselect package and custom selectors. Review their help files for details.

tidy selectors

everything(), all_of(), any_of(), starts_with(), ends_with(), contains(), matches(), num_range(), last_col()
cards selectors

all_ard_groups(), all_ard_variables()

Formula and List Selectors

Some arguments in the cards package accept list and formula notation, e.g. ard_continuous(statistic=). Below enumerates a few tips and shortcuts for using the list and formulas.

List of Formulas

Typical usage includes a list of formulas, where the LHS is a variable name or a selector.

ard_continuous(statistic = list(age ~ list(N = \(x) length(x)), starts_with("a") ~ list(mean = mean)))

Named List

You may also pass a named list; however, the tidyselect selectors are not supported with this syntax.
```
ard_continuous(statistic = list(age = list(N = \(x) length(x))))
```

Hybrid Named List/List of Formulas

You can pass a combination of formulas and named elements.

ard_continuous(statistic = list(age = list(N = \(x) length(x)), starts_with("a") ~ list(mean = mean)))

Shortcuts

You can pass a single formula, which is equivalent to passing the formula in a list.
```
ard_continuous(statistic = starts_with("a") ~ list(mean = mean)
```
As a shortcut to select all variables, you can omit the LHS of the formula. The two calls below are equivalent.
```
ard_continuous(statistic = ~list(N = \(x) length(x)))
ard_continuous(statistic = everything() ~ list(N = \(x) length(x)))
```

Combination Selectors

Selectors can be combined using the c() function.

ard_continuous(statistic = c(everything(), -age) ~ list(N = \(x) length(x)))