Template classes arma::Col in Rcpp Armadilllo

Dear fellow programmers,

in order to write a bootstrapped regression version for a seminar at university I tried to implement my R-version into Rcpp (this is for comparison of R to C++/Rcpp). However, I'm stuck with the error messages I receive, since I don't really understand those (the struggle of being new to C++ and especially Armadillo).

Here's the code I'm using. The first function is one I copied from the internet to get proper row-subsets of my matrix (in order to implement a proper non-parametric bootstrap):

    #include <RcppArmadillo.h>  // [[Rcpp::depends(RcppArmadillo)]]  // [[Rcpp::export]]    arma::mat testrows(arma::mat x, arma::Col idx) {    arma::mat xsub;    xsub = x.rows(idx-1);    return xsub;  }  

Furthermore, here's the code I wrote for my actual bootstrap version:

   #include <RcppArmadillo.h>  // [[Rcpp::depends(RcppArmadillo)]]  // [[Rcpp::export]]  arma::mat betaBoot(arma::colvec& y, const arma::mat& X, const int nboot) {      int n = X.n_rows, k = X.n_cols;      arma::mat betaHat(k,nboot);      for(int i = 0; i < nboot; i++){          Rcpp::NumericVector colId = Rcpp::runif(n, 0, (n-1));          arma::mat X_boot = testrows(X, colId);          arma::colvec y_boot = y(colId);          betaHat.col(i) = arma::solve(X_boot, y_boot);      }      return betaHat;  }  

betaHat is a matrix to contain the bootstrapped coefficient-vectors (in each column), the matrix should have dimension k x nboot. X_boot (within the loop) should be the bootstrapped data and y_boot the corresponding dependent observations. colId should be a random index for the bootstrapping procedure. Finally, betaHat should be returned.

attached you find a picture of the errors I receive when using sourceCpp.

Maybe it's something simple I just can't see or maybe the lack of experience, however learning this stuff would be great. So if you could help me with that, that would be great. Thank you in advance Erin

https://stackoverflow.com/questions/65433154/template-classes-armacol-in-rcpp-armadilllo December 24, 2020 at 10:08AM