[Rcpp-devel] repeatable random numbers

Zhongyi Yuan zhongyi-yuan at uiowa.edu
Thu Sep 1 21:23:38 CEST 2011

If there is a seed set in R before rngs() is called, then "RNGScope z;" can
be omitted, right?

I used to use RNGScope() to set seed. I guess that is not the right way, is

My test shows, with RNGScope(), even if I re-compile (without quitting R),
rngs always gives the same numbers. I have to quit R and then re-compile to
get random numbers. There is no such problem with "RNGScope z".


On Thu, Sep 1, 2011 at 12:15 PM, Dirk Eddelbuettel <edd at debian.org> wrote:

> I should have written that quick function as follows:
>   rngs <- cxxfunction(signature(), plugin="Rcpp",
>                        body="RNGScope z; return Rcpp::rnorm(5,0,1);")
> You _do_ want RNGScope around; my bad for omitting it in the previous post.
> Dirk
> --
> Two new Rcpp master classes for R and C++ integration scheduled for
> New York (Sep 24) and San Francisco (Oct 8), more details are at
> http://dirk.eddelbuettel.com/blog/2011/08/04#rcpp_classes_2011-09_and_2011-10
> http://www.revolutionanalytics.com/products/training/public/rcpp-master-class.php
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