[Rcpp-devel] Efficient DataFrame access by row & column

[Dirk Eddelbuettel]

On 19 February 2013 at 23:46, Ken Williams wrote:
| > From: Dirk Eddelbuettel [mailto:edd at debian.org]
| > You are relying on an implicit conversion here to make df(.,.) a double. The
| > compiler tells you that it is trying sugar operators.  Sugar is good to have in
| > Rcpp, but occassionally there is a cost. This may be one of those times.
| >
| > Try
| >
| >       double a = df(j,i);
| >       double b = df(j,last_i);
| >         if (fabs(a - b) > thresh) {
| >
| > and see if that works.
| 
| Unfortunately no, I get a similar error when I try that:
| 
| window.cpp:68:24: error: conversion from 'Rcpp::Vector<19>::Proxy {aka Rcpp::internal::generic_proxy<19>}' to 'double' is ambiguous
| window.cpp:68:24: note: candidates are:
| C:/mybin/R/R-2.15.2/library/Rcpp/include/Rcpp/vector/string_proxy.h:273:4: note: Rcpp::internal::generic_proxy<RTYPE>::operator int() const [with int RTYPE = 19]
| C:/mybin/R/R-2.15.2/library/Rcpp/include/Rcpp/vector/string_proxy.h:272:4: note: Rcpp::internal::generic_proxy<RTYPE>::operator bool() const [with int RTYPE = 19]
| C:/mybin/R/R-2.15.2/library/Rcpp/include/Rcpp/vector/string_proxy.h:267:26: note: Rcpp::internal::generic_proxy<RTYPE>::operator U() const [with U = double, int RTYPE = 19]

Maybe try std::fabs() instead of fabs() ?

That is one of the reasons I do not like a global 'using namespace Rcpp' in
my code.  Explicit namespaces are, well, explicit.

Dirk
| 
| 
| >
| > Not every conceivable operation is implemented in Rcpp,
| 
| Of course. =)
| 
| > but we are always
| > open to patches to make it more complete.
| 
| If I can get myself up to speed with my understanding, I'll be happy to contribute what I can.
| 
|  -Ken
| 
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-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com