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Extract Named Arguments from Dots with Defaults

Source: R/extractArgs.R
extractArgs.Rd

Utility to extract a subset of arguments from a list (typically list(...)) and merge them with default values. Elements of dots override entries in defaults of the same name; explicit NULL values are preserved.

Usage

extractArgs(dots, defaults, validate = NULL, returnRest = FALSE)

Arguments

dots

named list of arguments (usually list(...)).

defaults

named list of default values.

validate

optional validation function, called with the merged argument list for its side effect. It should throw an error on invalid input; its return value is ignored.

returnRest

logical; if TRUE, a list with components args (the merged arguments) and rest (all elements of dots not matching a default, including unnamed ones) is returned.

Value

named list of extracted arguments, or a list with components args and rest if returnRest = TRUE.

See also

Other pkg.args: callIf(), getDotsArg(), mergeArgs(), recycle()

Examples

dots <- list(col = "red", lwd = 2, 99)
extractArgs(dots, defaults = list(col = "black", lty = 1))
#> $col
#> [1] "red"
#> 
#> $lty
#> [1] 1
#> 

extractArgs(dots, defaults = list(col = "black", lty = 1),
            returnRest = TRUE)
#> $args
#> $args$col
#> [1] "red"
#> 
#> $args$lty
#> [1] 1
#> 
#> 
#> $rest
#> $rest$lwd
#> [1] 2
#> 
#> $rest[[2]]
#> [1] 99
#> 
#>