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rr-packageroxygen2

Do functions within a package share the same sub-functions?

I'm trying to understand how this package (darksky, found here: https://github.com/hrbrmstr/darksky) works.

It contains these two scripts in the R folder:

  1. aaa.R, and
  2. get-current-forecast.R

The former (aaa.R) contains a subfunction called convert_time. This is being called by the latter (get-current-forecast.R) and seems to work but aaa.R is not imported/refferred to by get-current-forecast.R.

How is this working? Are all subfunctions available to other functions in the same package?

Solution

  • Packages don't work the same as sourcing R files in an interactive session. All the functions defined in every .R file in a package are registered in the package's namespace, which gets attached when you run library(foo). So when a function in the package calls some other function, R first looks in that package's namespace for function by that name.

    However, functions defined inside another function are different. R won't see and register those in the package namespace. They would be available only within the enclosing function.

    For example,

    foo <- function(x){
  y <- x+1
  bar <- function(z){
    z+1
  }

  bar(y)
}

    If foo were defined in some .R file in a package, the function foo would be visible, but bar would be visible only within foo.