R help - Oct 2005 - Calling R functions from C

Dear R users,

I read on the "Introduction to the .C Interface to R" by Peng &
Leeuw
(http://www.biostat.jhsph.edu/~rpeng/docs/interface.pdf) that it is 
possible to use a few R functions (such as "dnorm") within C by 
including the "Rmath.h" header file in your C code:
e.g.

#include <R.h>
#include <Rmath.h>
void kernel_smooth(double *x, int *n, double *xpts, int *nxpts,
double *h, double *result)
{
int i, j;
double d, ksum;
for(i=0; i < *nxpts; i++) {
ksum = 0;
for(j=0; j < *n; j++) {
d = xpts[i] - x[j];
ksum += dnorm(d / *h, 0, 1, 0);
}
result[i] = ksum / ((*n) * (*h));
}
}


In the manual "Writing R extensions" there is also a list of special 
functions which can be called in C.

I was wondering whether there is a way to call any other R functions 
similarly. Is there any documented exemple available somewhere?

Thanks a lot for your help,

Florent

I'm curious, I realize there are methods for Type II and III sums of 
squares, and yet, when I've been constructing models with lm, I've 
noticed that position of the term of the model has not mattered in 
terms of its p-value.  Does lm use sequential Type I sums of squares, 
or something else?

Thanks!

-Jarrett