On 14 January 2014 at 16:40, boiled_wonderland wrote:
| What is the RcppArmadillo way to make binomial draws from a vector of probs,
| similar to what rbinom does in R?
1) It is pretty common list etiquette in these quarters to post with a name
and affiliation. You may find list member more willing to help you if
you adhere to common behaviour.
2) RcppArmadillo is a member of the Rcpp family; discussions for Rcpp and
related packages are happening at the rcpp-devel list. Conrad, the
Armadillo author, also reads that list.
3) RcppArmadillo is a wrapper for Armadillo, and
http://arma.sourceforge.net/docs.html
is the main source of documentation. You will see that Armadillo supports
from uniform and normal distributions.
4) Rcpp, however, supports just about all distributions which R supports.
So you can draw via Rcpp and instantiate an Armadillo object with the
values. At the C level, some distributions have an additional parameter
for degrees of freedom, the header file should be informative. Binomial
is easier. Here is a quick example just with Rcpp types:
R> cppFunction('NumericVector nb(int n) { return(rbinom(n,1,0.5));}')
R> set.seed(42); nb(4) # draw 4 via C++
[1] 1 1 0 1
R> set.seed(42); rbinom(4,1,0.5) # reset seed, draw 4 from R
[1] 1 1 0 1
R>
Dirk
--
Dirk Eddelbuettel | e...@debian.org | http://dirk.eddelbuettel.com
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