Source code of nlm function in stats package - r

Question

I need to find the source code of the nlm function.
When I use
edit(nlm)
below code appears
function (f, p, ..., hessian = FALSE, typsize = rep(1, length(p)),
fscale = 1, print.level = 0, ndigit = 12, gradtol = 1e-06,
stepmax = max(1000 * sqrt(sum((p/typsize)^2)), 1000), steptol = 1e-06,
iterlim = 100, check.analyticals = TRUE)
{
print.level <- as.integer(print.level)
if (print.level < 0 || print.level > 2)
stop("'print.level' must be in {0,1,2}")
msg <- (1 + c(8, 0, 16))[1 + print.level]
if (!check.analyticals)
msg <- msg + (2 + 4)
.External2(C_nlm, function(x) f(x, ...), p, hessian, typsize,
fscale, msg, ndigit, gradtol, stepmax, steptol, iterlim)
}
now when I want to see what is insode C_nlm
I tried
stats:::C_nlm
and I get
$name
[1] "nlm"
$address
<pointer: 0x0000000004a83920>
attr(,"class")
[1] "RegisteredNativeSymbol"
$dll
DLL name: stats
Filename: C:/Program Files/R/R-3.1.2/library/stats/libs/x64/stats.dll
Dynamic lookup: FALSE
$numParameters
[1] 11
attr(,"class")
[1] "ExternalRoutine" "NativeSymbolInfo"
After some web search I found out that I need to use grep after this.
But I am not getting how to use it.
I tried these references
How to locate code called by .External2()?
How can I view the source code for a function?
Can anyone please tell me how to proceed further?

Answer 1

You can browse the R source code at this GitHub repo: r-source.
Search it for the term "SEXP nlm" since stats:::C_nlm points to a function with the name "nlm" and all functions returning data to R use a datatype called SEXP (S expression).
You'll get two hits in the files statsR.h and optimize.c. The c-file is what you are looking for, so go down to the line starting with SEXP nlm and you got it.
SEXP nlm(SEXP call, SEXP op, SEXP args, SEXP rho)
{
SEXP value, names, v, R_gradientSymbol, R_hessianSymbol;
double *x, *typsiz, fscale, gradtl, stepmx,
steptol, *xpls, *gpls, fpls, *a, *wrk, dlt;
int code, i, j, k, itnlim, method, iexp, omsg, msg,
n, ndigit, iagflg, iahflg, want_hessian, itncnt;
/* .Internal(
* nlm(function(x) f(x, ...), p, hessian, typsize, fscale,
* msg, ndigit, gradtol, stepmax, steptol, iterlim)
*/
function_info *state;