Setting Object Attributes

Hadley Wickham — written Dec 10, 2012 — source

All R objects have attributes, which can be queried and modified with the attr method. Rcpp also provides a names() method for the commonly used attribute: attr("names"). The following code snippet illustrates these methods:

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
NumericVector attribs() {
  NumericVector out = NumericVector::create(1, 2, 3);

  out.names() = CharacterVector::create("a", "b", "c");
  out.attr("my-attr") = "my-value";
  out.attr("class") = "my-class";

  return out;
}

Here’s what the object we created in C++ looks like in R:

attribs()

a b c 
1 2 3 
attr(,"my-attr")
[1] "my-value"
attr(,"class")
[1] "my-class"

tags: basics

Extending R with C++ and Fortran — Dirk Eddelbuettel and JBrandon Duck-Mayr
Benchmarking Rcpp code with RcppClock — Zach DeBruine
Simulation Smoother using RcppArmadillo — Tomasz Woźniak