[Rcpp-devel] What is the most efficient method to check if a Rcpp vector contains an element?

[Romain Francois]

Thanks. 

In any case, for things like this the best thing to do is to not trust what anyone says and actually benchmark with realistic data. 

Romain

Le 31 déc. 2013 à 16:29, Hadley Wickham <h.wickham at gmail.com> a écrit :

>> I believe you are mistaken. sorting is an expensive O( N log(N) ) operation.
>> 
>> I’d use something like std::find (or std::any_of if you use C++11). Those
>> are O(N)
>> Otherwise, you might like Rcpp::any or Rcpp::any_of
> 
> It depends on the scenario - if you want to look up M values in a
> vector of length N, then sorting + binary search will be O(M log(N) +
> N log(N)) where scanning each time will be O(MN). If M = 1, there's no
> point presorting, but if it's large, it pays to sort first.
> 
> Hadley
> 
> -- 
> http://had.co.nz/