In tidyr: Tidy Messy Data

tidyselect implements a DSL for selecting variables. It provides helpers for selecting variables:

var1:var10: variables lying between var1 on the left and var10 on the right.
[starts_with("a")][tidyselect::starts_with]: names that start with "a".
[ends_with("z")][tidyselect::ends_with]: names that end with "z".
[contains("b")][tidyselect::contains]: names that contain "b".
[matches("x.y")][tidyselect::matches]: names that match regular expression x.y.
[num_range(x, 1:4)][tidyselect::num_range]: names following the pattern, x1, x2, ..., x4.
[all_of(vars)][tidyselect::all_of]/[any_of(vars)][tidyselect::any_of()]: matches names stored in the character vector vars. all_of(vars) will error if the variables aren't present; any_of(var) will match just the variables that exist.
[everything()][tidyselect::everything]: all variables.
[last_col()][tidyselect::last_col]: furthest column on the right.
[where(is.numeric)][tidyselect::where]: all variables where is.numeric() returns TRUE.

As well as operators for combining those selections:

!selection: only variables that don't match selection.
selection1 & selection2: only variables included in both selection1 and selection2.
selection1 | selection2: all variables that match either selection1 or selection2.