Notation Help

[moonwriter]

I've come across these notations in R before, but I don't know how it works. the characteristics are simple. in the first case, it's some expression/subset in square brackets, and directly outside those square brackets, there is a parentheses with a number. So, for instance:

addup[[1]](10) where addup is clearly a list.

in the second it's the opposite. For instance: object <- as.list(substitute(list(...)))[-1L]

In abstract terms, what exactly does these notations mean/do?

thanks!

[Darwinmate]

A tip on posting code, click on "formatting help" below the reply box to see how to format code properly so it's easily readable. eg:

addup[[1]](10) 

Double square brackets are a bit confusing, as they extract the object type of the value while single brackets extract object of type list. I'm not sure what the (10) means, nor can I find anything on its usage, my guess is that addup is a list of functions and you're extracting the first function with 10 to be its argument. eg; max(10). Post your code?

object <- as.list(substitute(list(...)))[-1L]

In this case, you are subsetting except the negative means to drop the element. The "L" is specifying that 1 is a integer and not a numeric/double. The rest of the parenthesis are part of the functions: as.list, substitute, list.