UseR!
Seamless R
and C++
Integration
with Rcpp
Dirk Eddelbuettel
Dirk Eddelbuettel
Seamless R and C++
Integration with Rcpp
123
Dirk Eddelbuettel
River Forest
Illinois, USA
ISBN 978-1-4614-6867-7 ISBN 978-1-4614-6868-4 (eBook)
DOI 10.1007/978-1-4614-6868-4
Springer New York Heidelberg Dordrecht London
Library of Congress Control Number: 2013933242
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To Lisa, Anna and Julia
Preface
Rcpp is an R add-on package which facilitates extending R with C++ functions.
It is being used for anything from small and quickly constructed add-on functions
written either to fluidly experiment with something new or to accelerate comput-
ing by replacing an R function with its C++ equivalent to large-scale bindings
for existing libraries, or as a building block in entirely new research computing
environments.
While still relatively new as a project, Rcpp has already become widely deployed
among users and developers in the R community. Rcpp is now the most popular
language extension for the R system and used by over 100 CRAN packages as well
as ten BioConductor packages.
This books aims to provide a solid introduction to Rcpp.
Target Audience
This book is for R users who would like to extend R with C++ code. Some famil-
iarity with R is certainly helpful; a number of other books can provide refreshers or
specific introductions. C++ knowledge is also helpful, though not strictly required.
An appendix provides a very brief introduction for C++ to those familiar only with
the R language.
The book should also be helpful to those coming to R with more of a C++ pro-
gramming background. However, additional background reading may be required to
obtain a firmer grounding in R itself. Chambers (2008) is a good introduction to the
philosophy behind the R system and a helpful source in order to acquire a deeper
understanding.
There may also be some readers who would like to see how Rcpp works inter-
nally. Covering that aspect, however, requires a fairly substantial C++ content and
is not what this book is trying to provide. The focus of this book is clearly on how
to
use
Rcpp.
vii
viii Preface
Historical Context
Rcpp first appeared in 2005 as a (fairly small when compared to its current size)
contribution by Dominick Samperi to the RQuantLib package started by Eddel-
buettel in 2002 (Eddelbuettel and Nguyen 2012). Rcpp became a CRAN pack-
age in its own name in early 2006. Several releases (all provided by Samperi) fol-
lowed in quick succession under the name Rcpp. The package was then renamed to
RcppTemplate; several more releases followed during 2006 under the new name.
However, no new releases were made during 2007, 2008, or most of 2009. Follow-
ing a few updates in late 2009, the RcppTemplate package has since been archived
on CRAN for lack of active maintenance.
Given the continued use of the package, Eddelbuettel decided to revitalize it.
New releases, using the original name Rcpp, started in November 2008. These in-
cluded an improved build and distribution process, additional documentation, and
new functionality—while retaining the existing “classic Rcpp” interface. While not
described here, this API will continue to be provided and supported via the Rcpp-
Classic package (Eddelbuettel and Franc¸ois 2012c).
Reflecting evolving C++ coding standards (see Meyers 2005), Eddelbuettel and
Franc¸ois started a significant redesign of the code base in 2009. This added numer-
ous new features, many of which are described in the package via different vignettes.
This redesigned version of Rcpp (Eddelbuettel and Franc¸ois 2012a) has become
widely used with over ninety CRAN packages depending on it as of November
2012. It is also the version described in this book.
Rcpp continues to be under active development, and extensions are being added.
The content described here shall remain valid and supported.
Related Work
Integration of C++ and R has been addressed by several authors; the earliest pub-
lished reference is probably Bates and DebRoy (2001). The “Writing R Extensions”
manual (R Development Core Team 2012d) has also been mentioning C++ and R
integration since around that time. An unpublished paper by Java et al. (2007)ex-
presses several ideas that are close to some of our approaches, though not yet fully
fleshed out. The Rserve package (Urbanek 2003, 2012) acts as a socket server for
R. On the server side, Rserve translates R data structures into a binary serialization
format and uses TCP/IP for transfer. On the client side, objects are reconstructed as
instances of Java or C++ classes that emulate the structure of R objects.
The packages rcppbind (Liang 2008), RAbstraction (Armstrong 2009a), and
RObjects (Armstrong 2009b) are all implemented using C++ templates. None of
them have matured to the point of a CRAN release. CXXR (Runnalls 2009)ap-
proaches this topic from the other direction: its aim is to completely refactor R on
a stronger C++ foundation. CXXR is therefore concerned with all aspects of the
R interpreter, read-eval-print loop (REPL), and threading; object interchange be-
Preface ix
tween R and C++ is but one part. A similar approach is discussed by Temple Lang
(2009a) who suggests making low-level internals extensible by package developers
in order to facilitate extending R. Temple Lang (2009b), using compiler output for
references on the code in order to add bindings and wrappers, offers a slightly dif-
ferent angle. Lastly, the rdyncall package (Adler 2012) provides a direct interface
from R into C language APIs. This can be of interest if R programmers want to ac-
cess lower-level programming interfaces directly. However, it does not aim for the
same object-level interchange that is possible via C++ interfaces, and which we
focus on with Rcpp.
Typographic Convention
The typesetting follows the usage exemplified both by the publisher, and by the
Journal of Statistical Software
.Weuse
• Sans-serif for programming language such as R or C++
• Boldface for (CRAN or other) software packages such as Rcpp or inline
• Courier for short segments of code or variables such as x<-y+z
We make use of a specific environment for the short pieces of source code inter-
woven with the main text.
River Forest, IL, USA Dirk Eddelbuettel
