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Decide where to get each argument to FUN

Source: R/matsindf_apply.R
where_to_get_args.Rd

The precedence rules for where to obtain values for the FUN argument to matsindf_apply() are codified here. The rules are:

  • Precedence order: ..., .dat, defaults arguments to FUN (highest priority to lowest priority).

  • If an element of ... is a character string of length 1, the element of ... provides a mapping between an item in .dat (with same name as the value of the character string of length 1) to an argument of FUN (with the same name as the name of the character string of length 1).

  • If the value of the character string of length 1 is not a name in .dat, the default arguments to FUN are checked in this order.

    • If the name of a default argument to FUN is the same as the value of the string of length 1 argument in ..., a mapping occurs.

    • If a mapping is not possible, the default arg to FUN is used directly.

Usage

where_to_get_args(.dat = NULL, FUN, ...)

Arguments

.dat

The .dat argument to matsindf_apply().

FUN

The FUN argument to matsindf_apply().

...

The ... argument to matsindf_apply().

Value

A named list wherein the names are the argument names to FUN. Values are character vectors with 2 elements. The first element is named source and provides the argument to matsindf_apply() from which the named argument should be found, one of ".dat", "FUN", or "...". The second element is named arg_name and provides the variable name or argument name in the source that contains the input data for the argument to FUN.

Examples

example_fun <- function(a = 1, b) {
  list(c = a + b, d = a - b)
}
# b is not available anywhere, likely causing an error later
matsindf:::where_to_get_args(FUN = example_fun)
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#> NULL
#> 
# b is now available in ...
matsindf:::where_to_get_args(FUN = example_fun, b = 2)
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>    "..."      "b" 
#> 
# b is now available in .dat
matsindf:::where_to_get_args(list(b = 2), FUN = example_fun)
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>   ".dat"      "b" 
#> 
# b now comes from ..., because ... takes precedence over .dat
matsindf:::where_to_get_args(list(b = 2), FUN = example_fun, b = 3)
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>    "..."      "b" 
#> 
# Mapping from c in .dat to b in FUN
matsindf:::where_to_get_args(list(c = 2),
                             FUN = example_fun, b = "c")
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>   ".dat"      "c" 
#> 
# Redirect from an arg in ... to a different default to FUN
matsindf:::where_to_get_args(FUN = example_fun, b = "a")
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>    "FUN"      "a" 
#> 
# b is found in FUN, not in .dat, because the mapping (b = "a")
# is not available in .dat
matsindf:::where_to_get_args(list(b = 2), FUN = example_fun, b = "a")
#> $a
#>   source arg_name 
#>    "FUN"      "a" 
#> 
#> $b
#>   source arg_name 
#>    "FUN"      "a" 
#>