[R] Finding code for R functions

From: Wolfrum, Ed <ed_wolfrum_at_nrel.gov>
Date: Wed 19 Oct 2005 - 07:26:33 EST


I am trying to figure out how to find the source code for R functions. I am specifically interested in finding the code for the "prcomp" function. I know that typing the function name without parenthesis will lead to the code (or to a .Internal or .FORTRAN or .C call). However, I don't really understand what is going on. For example, typing "mean" gives a "UseMethod" response, while typing "mean.default" give the actual code:

> mean

function (x, ...)
<environment: namespace:base>

> mean.default

function (x, trim = 0, na.rm = FALSE, ...) ---SNIP---
<environment: namespace:base>

Why is this? What does "mean.default" mean? I tried the same thing with "prcomp". With the stats package loaded, I cannot get to the source code for "prcomp".

> require(stats)

[1] TRUE
> prcomp

function (x, ...)
<environment: namespace:stats>
> prcomp.default

Error: object "prcomp.default" not found  

How do I find the prcomp code? Are there general rules for finding the source code for functions that I should know?

Thanks in Advance,

Edward J. Wolfrum, Ph.D.
National Renewable Energy Laboratory
Golden, Colorado

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