Data frames are one of R’s distinguishing features. Exposing a list of lists as an array of cases, they make many formal operations such as regression or optimization easy to represent. The R data.frame operation for lists is quite slow, in large part because it exposes a vast ...

Baptiste asked on StackOverflow about letting users supply C++ functions for use with Armadillo / RcppArmadillo. This posts helps with an extended answer. There is nothing specific about Armadillo here, this would the same way with Eigen, the GSL or any other library a user wants to support (and provides his ...

The RcppBDT package interfaces Boost.Date_Time with R. Both systems have their own date representations—and this provides a nice example of custom as() and wrap() converters. Here, we show a simplified example. We start with the forward declarations:

<span>#include <RcppCommon.h></span>

<span>#include <boost/date_time/gregorian/gregorian_types.hpp> 	</span><span>// Gregorian calendar types, no I/O</span>

<span>namespace</span> <span>Rcpp</span> <span>{</span>

    <span>// 'date' class boost::gregorian::date</span>
    <span>//</span>
    <span>// non-intrusive extension via template specialisation</span>
    <span>template</span> <span><></span> <span>boost</span><span>::</span><span>gregorian</span><span>::</span><span>date</span> <span>as</span><span>(</span><span>SEXP</span> <span>dt</span><span>);</span>
    <span>//</span>
    <span>// non-intrusive extension via template specialisation</span>
    <span>template</span> <span><></span> <span>SEXP</span> <span>wrap</span><span>(</span><span>const</span> <span>boost</span><span>::</span><span>gregorian</span><span>::</span><span>date</span> <span>&</span><span>d</span><span>);</span>
<span>}</span>

Given these forward declarations, we can now define the ...

Consider the following matrix

nr <span><-</span> nc <span><-</span> <span>6</span>
set.seed <span><-</span> <span>123</span>
m  <span><-</span> matrix<span>(</span>sample<span>(</span>c<span>(</span>rep<span>(</span><span>0</span><span>,</span><span>9</span><span>),</span> <span>1</span><span>),</span>nr<span>*</span>nc<span>,</span> replace<span>=</span><span>T</span><span>),</span> nrow<span>=</span>nr<span>,</span> ncol<span>=</span>nc<span>)</span>
sum<span>(</span>m<span>)</span><span>/</span>length<span>(</span>m<span>)</span>

[1] 0.1667

dimnames<span>(</span>m<span>)</span> <span><-</span> list<span>(</span>letters<span>[</span><span>1</span><span>:</span>nr<span>],</span> letters<span>[</span><span>1</span><span>:</span>nc<span>])</span>
m

a b c d e f a 0 0 0 0 0 1 b 0 0 0 1 0 1 c 0 0 0 0 0 0 d 0 0 0 0 0 0 e 1 1 0 0 0 0 f 0 0 0 1 0 0 This matrix can be coerced to a sparse matrix with

library<span>(</span><span>"Matrix"</span><span>)</span>

Loading required package: methods Loading required package: lattice

M1 <span><-</span> as<span>(</span>m<span>,</span> <span>"dgCMatrix"</span><span>)</span>
M1

6 x 6 sparse Matrix of class "dgCMatrix" a b c d e f ...

First, the median_Rcpp function is defined to compute the median of the given input vector. It is assumed that the input vector is unsorted, so a copy of the input vector is made using clone and then std::nth_element is used to access the nth sorted element. Since ...

The xts package by Jeff Ryan and Josh Ulrich is an immensely powerful tool that is widely used for timeseries work with R. Recently, the question about how to use it from Rcpp came up on StackOverflow and in a thread on the rcpp-devel list. In fact, xts has had ...

Two posts showed how to compute eigenvalues using Armadillo and using Eigen. As we also looked at using theGNU GSL, this post will show how to conpute eigenvalues using GSL. As mentioned in the previous GSL post, we instantiate C language pointers suitable for GSL (here the matrix M). Those ...

A recent post showed how to access the attributes of an xts object. We used an xts object as these are powerful and popular—but any R object using attributed could be used to illustrate the point. In this short post, we show how one can also do the inverse ...

In previous articles, we have seen that Rcpp can be particularly useful for simulations as it executes code at C++ speed. A very useful feature the API provided by R is the access to the R RNGs so that simulations at the C++ level can get precisely the same stream ...

We introduced Boost in a first post doing some integer math. In this post we want to look at the very versatile Boost.Lexical_Cast library to convert text to numbers – see the Motivation for more. As before, I should note that I write this post on a machine with ...

Boost is, to quote the quote by Sutter and Alexandrescu which adornes the Boost website, …one of the most highly regarded and expertly designed C++ library projects in the world. The impact of Boost on C++ cannot be overstated. Boost is, at its core, a collection of thoroughly designed and ...

One of the many features that make C++ different from C is exception handling. This is a somewhat big topic, and large codebases sometimes eschew exceptions for lack of traceability in truly large programs (and eg the Google in-house C++ style guide is a well-known example of the Just say ...