Well, For this particular use case why not just transform the parameters at the R level and then call the existing function? Is there not a closed form mapping?
~G On Jul 1, 2016 2:50 PM, "Joshua Ulrich" <josh.m.ulr...@gmail.com> wrote: > On Fri, Jul 1, 2016 at 6:13 AM, Luis Usier > <luis.henrique.us...@gmail.com> wrote: > > Gabriel, > > > > Thanks for that! I guess I really should have figured that one out > sooner, > > huh? > > > > I understand why that wouldn't be CRAN-compliant. But then, what *is* the > > proper way to do it? Is there any way I can call unexported functions > from > > another package and have it accepted by CRAN? > > > There may be ways to call unexported functions that R CMD check will > not detect, but you should not look for ways to violate the spirit of > the policy. Work-arounds include asking the package maintainer to > export the functionality you want, or you can copy the desired > functionality to your package (with attribution, of course). > > In this particular case, you can probably get what you want via the > Rmath library. It provides C-level access to all the distribution > functions (and more). You would need something like this in your C > code: > > #include <Rmath.h> > GetRNGstate(); > double rn = rnorm(0.0, 1.0); > PutRNGstate() > > Once Dirk recovers from useR!, he'll tell you how this is all > super-easy if you just use Rcpp. ;) > > > Also, if I instead re-write the random variable generating functions, do > > you have any idea of where the source code is in the stats package? As I > > said above, I can't seem to find the source code for the functional > forms. > > > See the sections "Functions that call compiled code" and "Compiled > code in a base package" from this answer: > http://stackoverflow.com/a/19226817/271616 > > That should give you a few pointers on where/how to look. > > > Thanks, > > > > Luis > > > > On Thu, Jun 30, 2016 at 10:38 PM, Gabriel Becker <gmbec...@ucdavis.edu> > > wrote: > > > >> Luis, > >> > >> C_rnorm is a symbol but it's not exported. This means that you *can* do > >> this by using stats:::C_rnorm. > >> > >> That said, it's not exported, which means that it's not supported to do > >> this. So your package likely would not be allowed on CRAN, for example. > >> > >> Best, > >> ~G > >> On Jun 30, 2016 2:08 PM, "Luis Usier" <luis.henrique.us...@gmail.com> > >> wrote: > >> > >>> Hi all, > >>> > >>> Looking at the body for the function rnorm, I see that the body of the > >>> function is: > >>> > >>> .Call(C_rnorm, n, mean, sd) > >>> > >>> I want to implement functions that generate normal (and other) random > >>> variables. Now, I understand that I can perfectly well just call the R > >>> wrapper for these functions and that will be almost indistinguishable > for > >>> most purposes, but for whatever reason I wanted to try and call the C > >>> function directly. My first instinct was to call them as: > >>> > >>> .Call(C_rnorm, 1, 1, 1) > >>> > >>> This doesn't work because R assumes C_rnorm is an object. Looking at > the > >>> documentation for .Call, I try passing it in as a string: > >>> > >>> .Call("C_rnorm", 1, 1, 1, PACKAGE = "stats") > >>> > >>> This doesn't work either. The help page links to getNativeSymbolInfo(), > >>> which I can't make work either. It also refers me to the dyn.load() > >>> function and the "Writing R Extensions" manual. > >>> > >>> After reading and trying to digest those, I try > >>> > >>> getDLLRegisteredRoutines("stats") > >>> > >>> which shows me all the C and Fortran functions as registered routines, > >>> along with their number of parameters. I retrieve rnorm from the list > and > >>> pass it on to .Call, which then works fine. > >>> > >>> However, is there an easier way to do this? Specifically, I would like > to > >>> call the DLL registered routines from within functions in a package I > am > >>> writing. The manual tells me I should use useDynLib(). So if I added > >>> useDynLib("stats") to my namespace, would that work? Could I then have > a > >>> function such as: > >>> > >>> function(x, y, z) .Call(C_rnorm, x, y, z) > >>> > >>> in my package? If not, what is the proper way of calling these > functions > >>> from other packages? Should I use "C_rnorm" or "norm"? > >>> > >>> Also, I was looking for the C source code of rnorm, because I wanted to > >>> understand how the function works. Looking at Winston Chang's github R > >>> mirror, I found rnorm in the random.c file in the stats package. > However, > >>> the code I find for it: > >>> > >>> > >>> > >>> #define DEFRAND2_REAL(name) \ > >>> SEXP do_##name(SEXP sn, SEXP sa, SEXP sb) { \ > >>> return random2(sn, sa, sb, name, REALSXP); \ > >>> } > >>> DEFRAND2_REAL(rnorm) > >>> > >>> > >>> Doesn't help me at all in understanding how it works. It should create > a > >>> function random2(sn, sa, sb, norm, REALSXP); I understand that is a > >>> version > >>> of the random2 function that returns a real S expression taking sn, sa > and > >>> sb as parameters. But how does find the actual functional form for the > >>> normal distribution? > >>> > >>> I am asking because I would like to rewrite some of the other > functions, > >>> such as parameterizing rbeta by the mean and sample size rather than by > >>> the > >>> number of successes and failures and rgamma by the mean and total time > >>> elapsed instead of the number of events. Once I understand how the C > >>> source > >>> code works, it would be hopefully not very difficult to reparameterize > >>> them. > >>> > >>> Thanks, > >>> > >>> Luis Usier > >>> > >>> [[alternative HTML version deleted]] > >>> > >>> ______________________________________________ > >>> R-devel@r-project.org mailing list > >>> https://stat.ethz.ch/mailman/listinfo/r-devel > >>> > >> > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- > Joshua Ulrich | about.me/joshuaulrich > FOSS Trading | www.fosstrading.com > R/Finance 2016 | www.rinfinance.com > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
