<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt">Thanks Christian and Dirk, I appreciate your help.<br>I am using sample() because in my real application probabilities for the members of the vector I want to sample from are not equal. <br>I'm happy and embarrassed to say that I figured out my problem. I should have provided a vector with values from 0 to max-1 to sample from, since I use it as an index later. Instead I used 1 to max as you would in R, so whenever max was one of the sampled elements it would result in an error.<br>Cheers,<br>Rahel<br> <br><div><span><br></span></div><div><br></div> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> <hr size="1"> <b><span
style="font-weight:bold;">Von:</span></b> Dirk Eddelbuettel <edd@debian.org><br> <b><span style="font-weight: bold;">An:</span></b> xian@unm.edu <br><b><span style="font-weight: bold;">CC:</span></b> rcpp-devel@lists.r-forge.r-project.org; Rahel Sollmann <rasrage@yahoo.de> <br> <b><span style="font-weight: bold;">Gesendet:</span></b> 10:50 Samstag, 27.Oktober 2012<br> <b><span style="font-weight: bold;">Betreff:</span></b> Re: [Rcpp-devel] problem with sample() implemented in Rcpp/RcppArmadillo<br> </font> </div> <br><br>On 27 October 2012 at 05:13, Christian Gunning wrote:<br>| > I am very new to c++ so I apologize in advance if this is a stupid question:<br>| <br>| I ran into this myself when I started using Rcpp -- it's a good<br>| question. The R API is extensive, but it's vanilla C and doesn't<br>| handle vectors (and you already know how to sample() a scalar,<br>| right?).<br><br>Someone should sit down and write a C++
variant of sample for Rcpp. Having a<br>starting point would help, others can then tune.<br><br>Personally, I don't have a need for one so no itch to scratch...<br> <br>| > For a larger analysis I am trying to implement the R function sample() in c++ via RcppArmadillo.<br>| <br>| There's a non-trivial penalty for reaching back into R for functions<br>| that aren't exported via the API (e.g. "Rcpp::Function sample =<br>| base["sample"];"). <br><br>Correct.<br><br>| Rcpp Vectors are STL containers, <br><br>Incorrect.<br><br>We make them look like STL containers by giving them begin(),<br>end(), ... member functions but they are still R objects ("SEXP") underneath.<br><br>That means in particular that the carefully crafted STL algos with their<br>performance guarantees will NOT have these guarantees.<br><br>That said, we can easily wrap genuine STL vectors so the rest of you argument<br>is good :)<br><br>| and many folk have asked the same
questions wrt the STL. There's some good<br>| background reading here:<br>| <a href="http://stackoverflow.com/questions/6942273/get-random-element-from-container-c-stl" target="_blank">http://stackoverflow.com/questions/6942273/get-random-element-from-container-c-stl</a><br><br>Nice reference, and "+1" for going back to standard STL functions and<br>behaviour which (in my not so humble opinions) is one of the best approaches<br>one can undertake when writing C++.<br><br>Dirk<br><br>-- <br>Dirk Eddelbuettel | <a ymailto="mailto:edd@debian.org" href="mailto:edd@debian.org">edd@debian.org</a> | <a href="http://dirk.eddelbuettel.com/" target="_blank">http://dirk.eddelbuettel.com</a> <br><br><br> </div> </div> </div></body></html>