你不能通过引用来做.但是，如果您返回数据框，它会起作用:

You cannot do it by reference. But if you return the data frame it works:

#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
DataFrame AddNewCol(const DataFrame& df, std::string new_var) {
  NumericVector vec_x = df["x"];
  NumericVector vec_y = df["y"];
  df[new_var] = vec_x * Rcpp::pow(vec_y, 2);
  return df;
}

/*** R
set.seed(42)
df <- data.frame(x = runif(10), y = runif(10))
AddNewCol( df ,"result")
*/

请注意，我冒昧地稍微简化了计算.结果:

Note that I have taken the liberty to simplify the computation a bit. Result:

> set.seed(42)

> df <- data.frame(x = runif(10), y = runif(10))

> AddNewCol( df ,"result")
           x         y      result
1  0.9148060 0.4577418 0.191677054
2  0.9370754 0.7191123 0.484582715
3  0.2861395 0.9346722 0.249974991
4  0.8304476 0.2554288 0.054181629
5  0.6417455 0.4622928 0.137150421
6  0.5190959 0.9400145 0.458687354
7  0.7365883 0.9782264 0.704861206
8  0.1346666 0.1174874 0.001858841
9  0.6569923 0.4749971 0.148232064
10 0.7050648 0.5603327 0.221371155