To cite Rcpp in publications use:

Dirk Eddelbuettel, Romain Francois (2011). Rcpp: Seamless R and C++ Integration. Journal of Statistical Software, 40(8), 1-18. URL http://www.jstatsoft.org/v40/i08/.

Corresponding BibTeX entry:

  @Article{,
    title = {{Rcpp}: Seamless {R} and {C++} Integration},
    author = {Dirk Eddelbuettel and Romain Fran\c{c}ois},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {40},
    number = {8},
    pages = {1--18},
    url = {http://www.jstatsoft.org/v40/i08/},
  }