How to search an environment using ls() inside a function?

问题

I want to find a set of functions and save them, because I want to send them to a remote server in an Rdata file, and I don't want to install a new package on the server.

Although I am getting an error using the approach below, easier / better approaches are welcome.

MWE:

Here are two dummy functions:

abcd.fun.1    <- function() return(1)
abcd.fun.2    <- function() return(2)

I can identify the dummy functions:

ls()[grep('abcd', ls())]

But when I wrap this in a function:

 find.test <- function(x) {
     return(ls()[grep(x, ls())])
 }
 find.test('abcd')

The function returns character(0)

Ultimately I would like to

 save(find.test('abcd'), file = test.Rdata)

回答1:

Why not use the pattern= argument to ls?
Calling ls inside a function lists the objects that exist within the function scope, not the global environment (this is explained in ?ls).

If you want to list the objects in the global environment from a function, specify envir=.GlobalEnv.

x <- 1:10
f <- function() ls()
g <- function() ls(envir=.GlobalEnv)
h <- function() ls(envir=.GlobalEnv, pattern="[fg]")
f()
# character(0)
g()
# [1] "f" "g" "h" "x"
h()
# [1] "f" "g"

回答2:

You need to tell your function to list objects in an environment other than itself, e.g. the global environment. (And while you're at it, you can also specify the regex pattern as an argument to ls.):

find.test <- function(x, envir=.GlobalEnv) {
  ls(pattern=x, envir=envir) 
}

See ?ls for more info about ls() and ?environment for other options to specify the environment.

来源：https://stackoverflow.com/questions/8142941/how-to-search-an-environment-using-ls-inside-a-function

标签

grep

environment