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

[Dirk Eddelbuettel]

Asis,

On 29 December 2013 at 09:26, Dirk Eddelbuettel wrote:
| On 29 December 2013 at 12:50, Asis Hallab wrote:
| | Should I convert my Rcpp Vector to a std::vector and do the above, as explained
| | on the stackoverflow blog?
| 
| You don't need to convert.  The STL types such as std::vector use iterators,
| and Rcpp was set up in such a way to make this possible.
| 
|    ## next line wrapped for mail, otherwise all on one line
|    R> cppFunction('bool contains(NumericVector X, double z) { 
|          return std::find(X.begin(), X.end(), z)!=X.end(); }')
|    R> contains(1:1e5,7777)
|    [1] TRUE
|    R> contains(1:1e5,-1)
|    [1] FALSE
|    R> 

For completeness, a solution using any() which Romain had reminded us about.
This is possibly a little more idiomatic for Rcpp vectors, and shorter:

    ## next line wrapped for mail, otherwise all on one line
    R> cppFunction('bool any(NumericVector X, double z) { 
                             return any(X.begin(), X.end(), z); }')
    R> any(1:1e5,7777)
    [1] TRUE
    R> any(1:1e5,-1)
    [1] FALSE
    R> 

Dirk

-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com