I sometimes meet the following code
foo <- function(x,y,...){
}
What is "..." ?
Is there any reference?
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1See section 10.4 of "An Introduction to R". (`help.start()`) – Edward Apr 18 '20 at 04:46
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it's varargs, if you're familiar with other languages – MichaelChirico Apr 18 '20 at 04:47
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1see https://stackoverflow.com/questions/3057341/how-to-use-rs-ellipsis-feature-when-writing-your-own-function – Suren Apr 18 '20 at 04:47
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1There's the `?"..."` help page (also called `?dots`) for the official reference. – MrFlick Apr 18 '20 at 05:16
1 Answers
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... is used to pass optional additional arguments to a function. Here is one example :
foo <- function(x, y, ...) paste(x, y, ...)
foo('a', 'bcd')
#[1] "a bcd"
foo('a', 'bcd', 'aaa')
#[1] "a bcd aaa"
foo('a', 'bcd', 'aaa', 'def')
#[1] "a bcd aaa def"
The documentation of this is present at ?"...".
Ronak Shah
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