[R] a Q re. read source files in spatial package.

[Yan Yu]

Hello,

I tried to read the source file related to variograms in the "spatial"
package.
I copied part of the source file of "spatial" package as follows,
in the follwing lines, I want to read "VR_variogram" function, from
wrapped in .C(), I suppose it is a C function..
I searched in various sub directories of R, but I could not seem to find
it..
DOes anyone know where can I find it?
thanks a lot in advance!
yan

-----------------------------------
    315 variogram <- function(krig, nint, plotit=TRUE, ...)
    316 {
    317   z <- .C("VR_variogram",
    318           xp = double(nint),
    319           yp = double(nint),
    320           nint = as.integer(nint),
    321           as.double(krig$x),
    322           as.double(krig$y),
    323           if(krig$np > 0) as.double(krig$wz) else
as.double(krig$z),
    324           as.integer(length(krig$x)),
    325           cnt = integer(nint),
    326           PACKAGE = "spatial"