[Rcpp-devel] data.frame from R to C++?

[deqiang sun]

Hi Dirk,

Thanks very much for your example. From this example I learned how to passing data back and forth between R and C++. 
The example is R code and uses piece of C++ code in side R program. 
Well, it's better if you put this example(by only making slight changes to make R embeded in C++) inside package RInside.

Accessing data by column name is the feature I ( and other people) usually want. 
However, is there a way to access the data Frame by row number?

Regards.

Dsun
On Apr 8, 2011, at 9:56 AM, Dirk Eddelbuettel wrote:

> 
> Ok, I now committed a slightly nice example to RcppExamples, a package I
> should revamp to contain more examples.  In there, we now receive a
> data.frame, operate on each column, create a new data and return old and new.
> 
> The core of the code (inside the try/catch protection) is
> 
>      // construct the data.frame object
>      Rcpp::DataFrame DF = Rcpp::DataFrame(Dsexp);
> 
>      // and access each column by name
>      Rcpp::IntegerVector a = DF["a"];
>      Rcpp::CharacterVector b = DF["b"];
>      Rcpp::DateVector c = DF["c"];
> 
>      // do something
>      a[2] = 42;
>      b[1] = "foo";
>      c[0] = c[0] + 7;                      // move up a week
> 
>      // create a new data frame
>      Rcpp::DataFrame NDF = 
> 	  Rcpp::DataFrame::create(Rcpp::Named("a")=a,
> 				  Rcpp::Named("b")=b,
> 				  Rcpp::Named("c")=c);
> 
>      // and return old and new in list
>      return(Rcpp::List::create(Rcpp::Named("origDataFrame")=DF,
> 				Rcpp::Named("newDataFrame")=NDF));
> 
> 
> Dirk
> -- 
> Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com