Hi Gregor, Dirk, Added here: https://github.com/RcppCore/Rcpp/commit/f6e7e34b94ba52c1341142a5640d0ede674073c7
Please feel free to tweak for wording / style / clarity :) Kevin On Mon, Mar 24, 2014 at 5:05 PM, Dirk Eddelbuettel <[email protected]> wrote: > > On 24 March 2014 at 16:45, Kevin Ushey wrote: > | Hi Gregor, > | > | This is probably worth a reminder as you say. Just for reference, the > | motivation is that R's internal computations for rexp and rgamma > | default to the 'scale' parameterization, rather than the 'rate' > | parameterization seen at the R level. Rcpp uses that internal > | operation and hence isn't consistent with what you see at the top > | level (even though it's consistent with the internals). > | > | R-exts does give this a bit of treatment in > | > http://cran.r-project.org/doc/manuals/r-release/R-exts.html#Distribution-functions. > | > | It's a bit awkward that the parameterizations differ at the R and C > | level, but it is what it is. > > Kevin beat me to it but that is what I was about to say. Rcpp sugar does > what the standalone R math library does (also at the C level). > > But you raise a good point, and we should add a note to the vignette. > > Dirk > > > | Cheers, > | Kevin > | > | On Mon, Mar 24, 2014 at 4:34 PM, Gregor Kastner <[email protected]> > wrote: > | > Dear all, > | > > | > I believe it's the second time I just realized that Rcpp::rgamma() behaves > | > differently than to R's rgamma() when called without named arguments: > | > > | > ********** BEGIN code.R ********** > | > > | > library(Rcpp) > | > > | > cppFunction(' > | > SEXP rgamma2(const int n, const double a, const double b) { > | > RNGScope scope; > | > return Rcpp::rgamma(n, a, b); > | > } > | > ') > | > > | > set.seed(123); > | > print(rgamma(1, 2, 3)); > | > > | > set.seed(123); > | > print(rgamma2(1L, 2, 3)); > | > > | > set.seed(123); > | > print(rgamma2(1L, 2, 1/3)); > | > > | > ********** END code.R ********** > | > > | > yields: > | > > | > [1] 0.2973645 > | > [1] 2.676281 > | > [1] 0.2973645 > | > > | > Maybe this is worth a tiny note in e.g. the "Rcpp syntactic sugar" > vignette? > | > Might save me (and possibly others) from realizing a third time. > | > > | > Best and thanks, > | > Gregor > | > _______________________________________________ > | > Rcpp-devel mailing list > | > [email protected] > | > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > | _______________________________________________ > | Rcpp-devel mailing list > | [email protected] > | https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > > -- > Dirk Eddelbuettel | [email protected] | http://dirk.eddelbuettel.com _______________________________________________ Rcpp-devel mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
