Compile-time action in R -

suppose have file foo.r , list of regular expressions in rex.txt. if put

rex <- paste(read.table("rex.txt", stringsasfactors=false)[[1]],collapse="|") 

into foo.r, variable rex initialized correctly when load foo.r using library(). same happens when compile foo.r foo.rc , load latter, good.

what want, however, literal value of variable rex included in foo.rc (when call cmpfile), i.e., when foo.rc loaded, variable rex initialised whatever in rex.txt @ compilation time, similar emacs lisp eval-when-compile (this way don't have copy rex.txt server run foo.rc).

is possible?

you can modify foo.r just before compilation, shown below.

test data:

text <- ' dosomething() rex <- paste(read.table("rex.txt", stringsasfactors=false)[[1]],collapse="|") dootherstuff() '  writelines(text,"foo.r") 

code:

foo <- readlines("foo.r")  pattern <- "^rex\\s*<-.*$"  eval(parse(text=grep(pattern, foo, value=true))[[1]])  newtext <- gsub(pattern, paste("rex <-",deparse(rex)), foo)  writelines(newtext,"foo.r") 

note eval() execute line rex <- ... create object in global environment, deparse() can find it. i'm assuming have 1 line matching pattern used.