[Rcpp-devel] Rcpp sugar preserving attributes

[Dirk Eddelbuettel]

Søren,

Happy New Year!

On 4 January 2015 at 09:53, Søren Højsgaard wrote:
| Dear all,
| 
| I have noticed an issue with preserving attributes (or rather attributes that are not preserved). Consider this code where I take the log of an array:

Quite possible. 

Attributes are just attached to objects, and we may well drop them along the
way.  Which is a bug.  Maybe you can start rewriting this in a way that
preserves attributes?  log is one of many 'math' functions implemented via
macro expansion so if you get it right for you get it right for many...

Dirk

| 
| #include <Rcpp.h>
| using namespace Rcpp;
| 
| //[[Rcpp::export]]
| NumericVector fun1(NumericVector x){
|   return log( x );
| }
| 
| //[[Rcpp::export]]
| NumericVector fun2(NumericVector x){
|   NumericVector out=clone(x), tmp=log(x);
|   for (int i=0;i<x.size();++i)out[i] = tmp[i];
|   return out;
| }
| 
| /*** R
| x <- HairEyeColor; x
| fun1(x)
| fun2(x)
|  */
| 
| 
| > fun1(x)
|  [1] 3.4657359 3.9702919 2.3025851 1.0986123 2.3978953 3.9120230 2.3025851 3.4011974 2.3025851 3.2188758 1.9459101
| [12] 1.6094379 1.0986123 2.7080502 1.9459101 2.0794415 3.5835189 4.1896547 2.7725887 1.3862944 2.1972246 3.5263605
| [23] 1.9459101 4.1588831 1.6094379 3.3672958 1.9459101 1.6094379 0.6931472 2.6390573 1.9459101 2.0794415
| 
| > fun2(x)
| , , Sex = Male
| 
|        Eye
| Hair        Brown      Blue     Hazel     Green
|   Black 3.4657359 2.3978953 2.3025851 1.0986123
|   Brown 3.9702919 3.9120230 3.2188758 2.7080502
|   Red   2.3025851 2.3025851 1.9459101 1.9459101
|   Blond 1.0986123 3.4011974 1.6094379 2.0794415
| 
| , , Sex = Female
| 
|        Eye
| Hair        Brown      Blue     Hazel     Green
|   Black 3.5835189 2.1972246 1.6094379 0.6931472
|   Brown 4.1896547 3.5263605 3.3672958 2.6390573
|   Red   2.7725887 1.9459101 1.9459101 1.9459101
|   Blond 1.3862944 4.1588831 1.6094379 2.0794415
| 
| fun2 is kludgy! Is there a more elegant way of preserving attributes using Rcpp sugar? 
| 
| All the best
| Søren
| 
| 
| 
| _______________________________________________
| Rcpp-devel mailing list
| Rcpp-devel at lists.r-forge.r-project.org
| https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel

-- 
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org