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This page the describes the <tidy-select> argument modifier which indicates the argument uses tidy selection (a special type of tidy evaluation). Tidy selection provides a concise DSL for selecting variables based on their names.

Overview of selection features

Tidyverse selections implement a dialect of R where operators make it easy to select variables:

  • : for selecting a range of consecutive variables.

  • ! for taking the complement of a set of variables.

  • & and | for selecting the intersection or the union of two sets of variables.

  • c() for combining selections.

In addition, you can use selection helpers. Some helpers select specific columns:

These helpers select variables by matching patterns in their names:

These helpers select variables from a character vector:

  • all_of(): Matches variable names in a character vector. All names must be present, otherwise an out-of-bounds error is thrown.

  • any_of(): Same as all_of(), except that no error is thrown for names that don't exist.

This helper selects variables with a function:

  • where(): Applies a function to all variables and selects those for which the function returns TRUE.

Indirection

There are two main cases:

  • If you have a character vector of column names, use all_of() or any_of(), depending on whether or not you want unknown variable names to cause an error, e.g unnest(df, all_of(vars)), unnest(df, !any_of(vars)).

  • If you want the user to supply a tidyselect specification in a function argument, you need to tunnel the selection through the function argument. This is done by embracing the function argument {{ }}, e.g unnest(df, {{ vars }}).

Learn more in vignette("programming.Rmd").