Expanding Lists

expand_list expands a named list with a given set of default items, if these are not already in the list, partially matching their names.

expand_list(x, ..., .exact = TRUE, .names = !.exact)

expand_dots(..., .exclude = NULL)

Arguments

x	input list
...	extra named arguments defining the default items. A list of default values can also be passed as a a single unnamed argument.
.exact	logical that indicates if the names in x should be partially matched against the defaults.
.names	logical that only used when .exact=FALSE and indicates that the names of items in x that partially match some defaults should be expanded in the returned list.
.exclude	optional character vector of argument names to exclude from expansion.

Value

a list

Functions

• expand_dots: expands the ... arguments of the function in which it is called with default values, using expand_list. It can only be called from inside a function.

Examples

expand_list(list(a=1, b=2), c=3)
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $c
#> [1] 3
#> 
expand_list(list(a=1, b=2, c=4), c=3)
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $c
#> [1] 4
#> 
# with a list
expand_list(list(a=1, b=2), list(c=3, d=10))
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $c
#> [1] 3
#> 
#> $d
#> [1] 10
#> 
# no partial match
expand_list(list(a=1, b=2, c=5), cd=3)
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $c
#> [1] 5
#> 
#> $cd
#> [1] 3
#> 
# partial match with names expanded
expand_list(list(a=1, b=2, c=5), cd=3, .exact=FALSE)
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $cd
#> [1] 5
#> 
# partial match without expanding names
expand_list(list(a=1, b=2, c=5), cd=3, .exact=FALSE, .names=FALSE)
#> $a
#> [1] 1
#> 
#> $b
#> [1] 2
#> 
#> $c
#> [1] 5
#> 

# works also inside a function to expand a call with default arguments
f <- function(...){
  cl  <- match.call()
  expand_list(cl, list(a=3, b=4), .exact=FALSE)
}
f()
#> f(a = 3, b = 4)
f(c=1)
#> f(c = 1, a = 3, b = 4)
f(a=2)
#> f(a = 2, b = 4)
f(c=1, a=2)
#> f(c = 1, a = 2, b = 4)

# expanding dot arguments

f <- function(...){ 
  expand_dots(list(a=2, bcd='a', xxx=20), .exclude='xxx') 
}

# add default value for all arguments 
f()
#> $a
#> [1] 2
#> 
#> $bcd
#> [1] "a"
#> 
# add default value for `bcd` only
f(a=10)
#> $a
#> [1] 10
#> 
#> $bcd
#> [1] "a"
#> 
# expand names
f(a=10, b=4)
#> $a
#> [1] 10
#> 
#> $bcd
#> [1] 4
#>