Why do I get the error for using “pnorm” in Rcpp

Question

I need to involve variable from arma::in my Rcpp code. But I ran into a problem when trying to use the sugar function pnorm. Here is a demo:

Answer 1

The Rcpp sugar functions are meant for vector type arguments like Rcpp::NumericVector. For scalar arguments you can use the functions in the R namespace:

#include 
#include 
// [[Rcpp::depends(RcppArmadillo)]]
using namespace Rcpp;

// [[Rcpp::export]]
double pget(NumericVector x, NumericVector beta) {
  arma::colvec xx = Rcpp::as(x) ;
  arma::colvec bb = Rcpp::as(beta) ;
  double tt = as_scalar( arma::trans(xx) * bb);
  double temp = R::pnorm(tt, 0.0, 1.0, 1, 0);
  return temp;
}

/*** R
x <- rnorm(5)
beta <- rnorm(5)
pget(x, beta)
*/

BTW, here two variants. First variant uses arma instead of Rcpp vectors as arguments. Since these are const references, no data is copied. In addition, arma::dot is used:

// [[Rcpp::export]]
double pget2(const arma::colvec& xx, const arma::colvec& bb) {
  double tt = arma::dot(xx, bb);
  return R::pnorm(tt, 0.0, 1.0, 1, 0);
}

The second variant calculates the scalar product without resorting to Armadillo:

// [[Rcpp::export]]
double pget3(NumericVector x, NumericVector beta) {
  double tt = Rcpp::sum(x * beta);
  return R::pnorm(tt, 0.0, 1.0, 1, 0);
}