CODEWITHSUNDEEP
r
qfazille
qfazille

Reputation: 1671

R function get rid of unused parameters in

I have a main function mainFunction that calls sub-functions :

Ideally I would like not to set manually all the "sub" parameters names in my mainFunction signature but use the ... instead. However I get the unused argument error :

# Initial try
subFunctionA <- function(a = 1, b = 2) {a+b}
subFunctionB <- function(aa = 1, bb = 2) {aa+bb}
subFunctionC <- function(a = 1, bb = 2) {a+bb}

mainFunction <- function(...) {
  x1 <- subFunctionA(...)
  x2 <- subFunctionB(...)
  x3 <- subFunctionC(...)
  x1+x2+x3
}

mainFunction(a = 2, b = 2, aa = 3, bb = 4)
# Return error "Error in subFunctionA(...) : arguments inutilisés (aa = 3, bb = 4)"

Below the workaround I use, but I'm not sure I make good practice of additional parameters :

# Workaround
parameters_filters <- function(fun, ...) {
  p <- list(...)
  p[which(names(p) %in% names(as.list(args(fun))))]
}

mainFunction_workaround <- function(...) {
  x1 <- do.call(subFunctionA, parameters_filters(subFunctionA, ...))
  x2 <- do.call(subFunctionB, parameters_filters(subFunctionB, ...))
  x3 <- do.call(subFunctionC, parameters_filters(subFunctionC, ...))
  x1+x2+x3
}

mainFunction_workaround(a = 2, b = 2, aa = 3, bb = 4)
# Returns 17

Is there a "cleaner" way to do so ?

Upvotes: 0

Views: 67

Answers (1)

Roland
Roland

Reputation: 132706

You were almost there with the initial try:

subFunctionA <- function(a = 1, b = 2, ...) {a+b}
subFunctionB <- function(aa = 1, bb = 2, ...) {aa+bb}
subFunctionC <- function(a = 1, bb = 2, ...) {a+bb}

mainFunction <- function(...) {
  x1 <- subFunctionA(...)
  x2 <- subFunctionB(...)
  x3 <- subFunctionC(...)
  x1+x2+x3
}

mainFunction(a = 2, b = 2, aa = 3, bb = 4)
#[1] 17

This will cause issues if the user uses positional arguments:

mainFunction(2, 2, 3, 4)
#[1] 12

Thus, I would avoid ... in the main function (unless you actually have optional parameters):

mainFunction <- function(a, b, aa, bb) {
  args <- list(a = a, b = b, aa = aa, bb = bb)
  x1 <- do.call(subFunctionA, args)
  x2 <- do.call(subFunctionB, args)
  x3 <- do.call(subFunctionC, args)
  x1+x2+x3
}

mainFunction(2, 2, 3, 4)
#[1] 17

And of course, not using ... here at all would be the safest option.

Upvotes: 1

Related Questions