Le 27/05/10 17:24, Vinh Nguyen a écrit :
Two questions:
1. The main difference when using RcppArmadillo and Rcpp is the
header declaration and the return type for the function right?
extern "C" SEXP fastLm(SEXP ys, SEXP Xs) {}
RcppArmadillo takes this extern stuff whereas Rcpp takes RcppExport?
RcppExport SEXP newRcppVectorExample(SEXP vector) {}
RcppExport is a macro that expands to extern "C". so you can use the one
you prefer, it makes no difference.
Many tutorials online explain what extern "C" means, and also writing R
extensions.
2. From the example, if I update the elements of X or Xr, then both
are updated correct? Because they are pointing to the same thing.
Just want to make sure. I'm dealing with both since Xr is used to
deal with some R objects, and X is used to do matrix multiplication,
etc.
arma::mat X(Xr.begin(), n, k, false); // reuses memory and
avoids extra copy
arma::colvec y(yr.begin(), yr.size(), false);
using this constructor of arma::mat, X only borrows the memory of Xr.
So when you update one, the other is also updated. see the documentation
of armadillo.
Thanks.
Vinh
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