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?
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.