On 22/03/2009 5:05 PM, JiHO wrote:
Hello everyone,
I often create some local "libraries" of functions (.R files with only
functions in them) that I latter call. In scripts that call a function
from such library, I would like to be able to test whether the
function is already known in the namespace and, only if it is not,
source the library file. I.e. what `require` does for packages, I want
to do with my local functions.
That's pretty hard to make bulletproof. Why not just put those
functions in a package, and use that package? If the functions are all
written in R, creating the package is very easy: see package.skeleton.
(And if you have a perfect memory and don't plan to distribute the
package to anyone, you can skip documenting the functions: then it's
almost no work at all.)
Duncan Murdoch
Example:
lib.R
foo <- function(x) { x*2 }
script.R
require.local(foo,"lib.R")
# that searches for function "foo" and, if not found, executes
source("lib.R")
foo(2)
Obviously, I want the test to be quite efficient otherwise I might as
well source the local library every time. I am aware that it would
probably not be able to check for changes in lib.R (i.e. do
complicated things such as re-source lib.R if foo in the namespace and
foo in lib.R are different), but that I can handle manually.
This seems like a common enough workflow but I cannot find a pre-
existing solution. Does anyone have pointers?
Otherwise I tried to put that together:
require.local <- function(fun, lib)
#
# Searches for function "fun" and sources "lib" in
# case it is not found
#
{
if (! (deparse(substitute(fun)) %in% ls(".GlobalEnv") && class(fun)
== "function") ) {
cat("Sourcing", lib,"...\n")
source(lib)
}
}
but I am really not confident with all those deparse/substitute things
and the environment manipulation, so I guess there should be a better
way.
JiHO
---
http://jo.irisson.free.fr/
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