How do you determine the namespace of a function?

Given a function, how do you determine which namespace it has come from?

For example, if I type mean.default at the command prompt, the output includes the fact that it is in the base package. I want to be able to do something like getNamespace(mean.default) and have it return "base" (or the actual base environment).

There is a getNamespace function but seems to only accept package names rather than function names.

print.function uses internal code to retrieve the namespace. I got as far as browsing do_printfunction in src/main/print.c but then gave up.

Solution 1:

I very recently learned about find() which seems to do just this.

R> find("ls")
[1] "package:base"
R> find("na.locf")
[1] "package:zoo"

Solution 2:

You want getNamespaceName + environment:

getNamespaceName(environment(mean.default))
# [1] "base"

Solution 3:

findFunction is another option and ?findFunction says you should use it instead of find with mode="function". The result of findFunction is a list of the environment(s) where the visible versions of the function are located.

Solution 4:

This function searches functions in the loaded namespaces and global environment:

getEnvName <- function(f) {
    attached <- c(environmentName(.GlobalEnv), loadedNamespaces())
    envs <- c(.GlobalEnv, lapply(attached[-1], .getNamespace))
    attached[vapply(envs, function(env) exists(f, env, inherits = FALSE), logical(1))]
}
median <- function() {}
getEnvName("median")
#> [1] "R_GlobalEnv" "stats"
getEnvName(".try_quietly")
#> [1] "tools"
getEnvName("getEnvName")
#> [1] "R_GlobalEnv"