Unpacks or binds values into the calling environment. Uses bquote escaping. NULL is a special case that is unpacked to all targets. NA targets are skipped. All non-NA target names must be unique.

unpack(wrapr_private_value, ...)

Arguments

wrapr_private_value

list of values to copy

...

argument names to write to

Value

value passed in (invisible)

Details

Note: when using []<- notation, a reference to the unpacker object is written into the unpacking environment as a side-effect of the implied array assignment. := assigment does not have this side-effect. Array-assign form can not use the names: ., wrapr_private_self, value, or unpack. Function form can not use the names: . or wrapr_private_value. For more details please see here http://www.win-vector.com/blog/2020/01/unpack-your-values-in-r/.

Related work includes Python tuple unpacking, zeallot's arrow, and vadr::bind.

Examples

# named unpacking # looks like assignment: DESTINATION = NAME_VALUE_USING d <- data.frame(x = 1:2, g=c('test', 'train'), stringsAsFactors = FALSE) unpack[train_set = train, test_set = test] := split(d, d$g) # train_set and test_set now correctly split print(train_set)
#> x g #> 2 2 train
print(test_set)
#> x g #> 1 1 test
rm(list = c('train_set', 'test_set')) # named unpacking NEWNAME = OLDNAME implicit form # values are matched by name, not index unpack[train, test] := split(d, d$g) print(train)
#> x g #> 2 2 train
print(test)
#> x g #> 1 1 test
rm(list = c('train', 'test')) # function version unpack(split(d, d$g), train, test) print(train)
#> x g #> 2 2 train
print(test)
#> x g #> 1 1 test
rm(list = c('train', 'test')) # pipe version split(d, d$g) %.>% unpack(., train, test) print(train)
#> x g #> 2 2 train
print(test)
#> x g #> 1 1 test
rm(list = c('train', 'test')) # Note: above is wrapr dot-pipe, piping does not currently work with # magrittr pipe due to magrittr's introduction of temporary # intermediate environments during evaluation. # bquote example train_col_name <- 'train' test_col_name <- 'test' unpack(split(d, d$g), train = .(train_col_name), test = .(test_col_name)) print(train)
#> x g #> 2 2 train
print(test)
#> x g #> 1 1 test
rm(list = c('train', 'test'))