Can someone explain what a placeholder is and how to use it in R programming?

CodePudding user response：

A pipe operator was introduced in R 4.1. The placeholder _ is a new way of referring to the data in the LHS of the pipe operator in the RHS of a pipe. It was introduced in R 4.2.0 and

• The placeholder refers to the data set in the LHS of a pipe instruction;
• can only be used in the RHS of a pipe instruction;
• can only be used with a named argument;
• can only be used once;
• it's not needed if it is the first argument of the RHS function, only as a placeholder for a 2nd, 3rd, etc argument.

See help('|>') and this r-devel thread.

Example:

mtcars |> row.names() |> grep("Merc", x = _)
#> [1]  8  9 10 11 12 13 14

^{Created on 2022-04-25 by the reprex package (v2.0.1)}