[R] simple addition in R, now fast & easy!

From: Joel Bremson <joel3000_at_gmail.com>
Date: Fri 29 Apr 2005 - 07:41:01 EST

At last, simple addition in R is now fast and easy!!!

They said it could never be done, but they've never heard of Fortran.

In order to add two numbers in R before you had to type:

> 7 + 3

It was tedious to type and several hours could pass as you waited for your return value.

So, imagine the excitement around your lab or office when you type in:


and get your result back faster then a greased goat!

Well now you can!

Here's how:

First create a file called add.f with the following code:


c Add two numbers

subroutine add(a,b,c)
double precision a,b,c
c = a + b

------------------end clip------------------------------

Don't disturb the spacing, Fortran is fussy about that.

Now compile you're code:

g77 -c add.f

Now make a shared lib for R (unix/linux):


This will create a file called 'add.so'

Now go into R:

>dyn.load("add.so") # you might need an explicit path here

And now you too have the power of fast, easy, simple addition!!


If you want to get real fancy you can put your .Fortran call into a function:

myadd = function(a,b){
out = .Fortran("add",as.numeric(a),as.numeric(b),c=as.numeric(0)) return(out$c)

> x = myadd(3,7)

[1] 10

And you've done it! Be vanquished naysayers, simple addition will trouble us no more!

(I thought a very simple tutorial on integrating Fortran code into R might be of use.)

Joel Bremson
Statistics Graduate Student
UC Davis

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