Make a user-created function in R

Question

I'm sorry if this has been asked before but I can't find the answer.

Let's say I write a small function in R

add2<-function(a){
return(a+2)
}

I save it as add2.R in my home directory (or any directory). How do I get R to find it??

> add2(4)
Error: could not find function "add2"

I know I can open up the script, copy/paste it in the console, run it, and then it works. But how do I get it built-in so if I open and close R, it still runs without me copying and pasting it in?

you can `source` things in your `.Rprofile` if you always want the function, or put it into a package and use `library`. — Justin, Jan 18 '13 at 16:35
Just to expand slightly on Justin's comment, the documentation at `?Startup` is a bit of a dense read, but it contains the essentials of how to use a `.RProfile` file. Basically, it "is searched for in the current directory or in the user's home directory (in that order). The user profile file is sourced into the workspace.". — joran, Jan 18 '13 at 16:45
windows 7 won't let me make a file called '.Rprofile'. Any suggestions? — stuppie, Jan 18 '13 at 17:10
Well, I did it in the command line.. move g.Rprofile .Rprofile stupid windows...... — stuppie, Jan 18 '13 at 17:17
Also, from within R you can do `file.create(".Rprofile")` --- even on Windows =). — Josh O'Brien, Jan 19 '13 at 01:31
Save the function using `save(add2, file = "add2.RData")` then load it when required `load("add2.RData")` — Seanosapien, Oct 30 '18 at 12:24

score 20 · Accepted Answer · edited May 23 '17 at 12:17

One lightweight option:

dump("add2", file="myFunction.R")

## Then in a subsequent R session
source("myFunction.R")

An alternative:

save("add2", file="myFunction.Rdata")

## Then just double click on "myFunction.Rdata" to open  
## an R session with add2() already in it 

## You can also import the function to any other R session with
load("myFunction.Rdata")

Until you're ready to package up functions into your own private package, storing them in well organized, source()-ready text files (as in the 1st example above) is probably the best strategy. See this highly up-voted SO question for some examples of how experienced useRs put this approach into practice.

score 4 · Answer 2 · answered Jan 18 '13 at 16:38

Before invoking the function (e.g. at the beginning of the script), you should source the file containing your user defined function/s, i.e. :

source("add2.R") # this executes add2.R script loading add2 function

Basically, source function executes the code included in the script passed as argument. So if the file contains only functions definitions it loads the function in memory for future use.

score 4 · Answer 3 · edited Jan 27 '13 at 04:19

If you want to start it automatically, then you have to set-up startup script and then use one of the methods outlined in answers above.

/Library/Frameworks/R.framework/Versions/2.15/Resources/etc/ is(for mac) the location of Rprofile.site, which must be edited adequately.

My version of it is:

.First <- function()
{ 
    dir='~/Desktop/Infobase/R/0_init/0_init.R'
    if(file.exists(dir))
    {
    source(dir, chdir = TRUE) 
    } else {cat("startup file is not found at:",dir)}
    cat("\nWelcome at", date(), "\n")
}    

.Last <- function()
{ 
cat("\nGoodbye at ", date(), "\n")
}

Note, that after you have sourced 1 R script, you do not need to enter this file anymore. Just do all you need from the file you sourced. In my case file "0_init.R" contains no functions, it just contains loading of other scripts. Well, you've got the idea.

Also, if you are doing this I recommend you to store them in new environment. Actual environments are not really suitable for your own functions(They are better implemented if you have a package developed, otherwise you lose a lot of control).

use "attach", "detach", "search", etc....

attach(FUN,name="af2tr")

Make a user-created function in R

3 Answers3