Rcpp data.frame issue

rcppdf.Rmd

---
title: "Rcpp Dataframe issue"
output: github_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

```{r}
fun <- Rcpp::cppFunction('
List DataFrameExample() {
  Rcpp::IntegerVector a = {1, 2, 3};
  
  // create a new data frame
  Rcpp::DataFrame DF = Rcpp::DataFrame::create(
    Rcpp::Named("a1")=a
	);

	Rcpp::DataFrame NDF = clone(DF);
	
	//NDF.push_back(a, "a2");
	NDF["a2"] = a;

  return(Rcpp::List::create(
    Rcpp::Named("origDataFrame")=DF,
  	Rcpp::Named("newDataFrame")=NDF)
  );
}')

dfs <- fun()
dfs

lapply(dfs, class)
lapply(dfs, attributes)

```