[Rcpp-devel] Rcpp sugar preserving attributes

[Søren Højsgaard]

Thanks! Probably a stupid question, but where are these functions defined? In math.h I see

VECTORIZED_MATH_1(log,::log)

but - where to look for the implementation?

Cheers
Søren


|-----Original Message-----
|From: Dirk Eddelbuettel [mailto:edd at debian.org]
|Sent: 4. januar 2015 16:32
|To: Søren Højsgaard
|Cc: rcpp-devel at lists.r-forge.r-project.org
|Subject: Re: [Rcpp-devel] Rcpp sugar preserving attributes
|
|
|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
||
||
||
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|
|--
|http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org