问题
I want to call a function but depending on the situation I might call it with extra arguments or not. Here is a simple example:
FUN <- function(arg1 = "default1", arg2 = "default2", arg3 = "default3")
print(list(arg1, arg2, arg3))
x1 <- "hi"
x2 <- TRUE
x3 <- 1:3
use.arg3 <- FALSE # This will decide if `x3` is used or not.
if (use.arg3) {
FUN(arg1 = x1, arg2 = x2, arg3 = x3)
} else {
FUN(arg1 = x1, arg2 = x2)
}
While the code is clear, it feels a little redundant. Also imagine that if I had similar use.arg1
and use.arg2
variables, I would have an ugly mix of possibilities (8)...
I have a solution posted below but I find it a little complicated, to the point that I always struggle to remember the exact syntax.
If you have a better idea, thank you for sharing.
回答1:
One solution is to use do.call
after building a list with the proper arguments:
do.call(FUN, c(list(arg1 = x1, arg2 = x2), # unconditional args
list(arg3 = x3)[use.arg3])) # conditional arg
And it generalizes well to multiple conditions:
do.call(FUN, c(list(arg1 = x1)[use.arg1] # conditional arg
list(arg2 = x2)[use.arg2] # conditional arg
list(arg3 = x3)[use.arg3])) # conditional arg
回答2:
Continuing the discussion from the comments on flodel's answer, here's an extension of my idea, out of curiosity. Not sure if it's really a feasible option:
FUN(arg1 = x1, arg2 = x2, arg3 = if(use.arg3) x3 else formals(FUN)$arg3)
来源:https://stackoverflow.com/questions/13992367/conditional-inclusion-of-arguments-in-a-function-call