R .Internal for Beginners

Question

I am new to R and I ran into a piece of code that I do not understand. More specifically, I would like to know what .Internal does. Here is an example that I am trying to convert to Matlab:

dunif <- function (x, min = 0, max = 1, log = FALSE) 
.Internal(dunif(x, min, max, log))
<environment: namespace:stats>

I would like to know what .Internal and <environment ... > do.

Thank you much in advance, Simon

See also http://stackoverflow.com/questions/1439348/how-to-examine-the-code-of-a-function-in-r-thats-object-class-sensitive/1444512 — Richie Cotton, Jul 29 '11 at 14:46
For this specific example it may be helpful to know that the answer is just `1/(max-min)` — Ben Bolker, Jul 29 '11 at 14:50

score 20 · Answer 1 · answered Jul 29 '11 at 14:38

From ?.Internal:

 ‘.Internal’ performs a call to an internal code which is built in
 to the R interpreter.

You'll find the code for dunif in the R sources. I find this type of function via a grep for it in main/names.c then grep for the name it refers to (do_math3 in this case), which you will find in main/arithmetic.c.

<environment: namespace:stats> simply tells you the location / namespace of the function.

score 4 · Answer 2 · answered Jul 29 '11 at 17:57

4

I found R in a Nutshell a useful resource to explain objects and environments in a non-intimidating way. It is worth a look.

answered Jul 29 '11 at 17:57

John

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R .Internal for Beginners

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