gnu: Add r-rcpp.

* gnu/packages/statistics.scm (r-rcpp): New variable.

gnu/packages/statistics.scm

@@ -266,3 +266,28 @@ (define-public r-munsell
      "The Munsell package contains Functions for exploring and using the
 Munsell colour system.")
     (license license:expat)))
+
+(define-public r-rcpp
+  (package
+    (name "r-rcpp")
+    (version "0.12.0")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append "mirror://cran/src/contrib/Rcpp_"
+                           version ".tar.gz"))
+       (sha256
+        (base32 "182109z0yc1snqgd833ssl2cix6cbq83bcxmy5344b15ym820y38"))))
+    (build-system r-build-system)
+    (home-page "http://www.rcpp.org")
+    (synopsis "Seamless R and C++ Integration")
+    (description
+     "The Rcpp package provides R functions as well as C++ classes which offer
+a seamless integration of R and C++.  Many R data types and objects can be
+mapped back and forth to C++ equivalents which facilitates both writing of new
+code as well as easier integration of third-party libraries.  Documentation
+about Rcpp is provided by several vignettes included in this package, via the
+'Rcpp Gallery' site at <http://gallery.rcpp.org>, the paper by Eddelbuettel
+and Francois (2011, JSS), and the book by Eddelbuettel (2013, Springer); see
+'citation(\"Rcpp\")' for details on these last two.")
+    (license license:gpl2+)))