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Which functions in R base call internal code?

14th September, 2010 4 comments

In a recent question on Stack Overflow about speeding up group-by operations, Marek wondered which functions called .Internal code (and consequently were fast). I was surprised to see that there appears to be no built-in way to check whether or not this is the case (though is.primitive is available for primitive functions).

Writing such a function is quite straight forward. We simply examine the contents of the function body, and search for the string “.Internal” within it.

callsInternalCode <- function(fn)
{
+++if(!require(stringr)) stop("stringr package required")
+++any(str_detect(capture.output(body(fn)), "\\.Internal"))
}

You can retrieve all the functions in the base package with this one-liner taken from an example on the Filter help page.

funs <- Filter(is.function, sapply(ls(baseenv()), get, baseenv()))

Now getting the list of functions that call internal code is easy.

names(funs)[sapply(funs, callsInternalCode)]
[1] "abbreviate" "agrep"
[3] "all.names" "all.vars"
[5] "anyDuplicated.default" "aperm"
...

EDIT: Tweaked the regex (the ‘.’ should have been escaped.)

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