| Title: | Examples using 'Rcpp' to Interface R and C++ |
| Version: | 0.1.10 |
| Date: | 2025-03-17 |
| Description: | Examples for Seamless R and C++ integration The 'Rcpp' package contains a C++ library that facilitates the integration of R and C++ in various ways. This package provides some usage examples. Note that the documentation in this package currently does not cover all the features in the package. The site https://gallery.rcpp.org regroups a large number of examples for 'Rcpp'. |
| Imports: | Rcpp |
| LinkingTo: | Rcpp |
| URL: | https://github.com/eddelbuettel/rcppexamples, https://dirk.eddelbuettel.com/code/rcpp.examples.html |
| BugReports: | https://github.com/eddelbuettel/rcppexamples/issues |
| License: | GPL-2 | GPL-3 [expanded from: GPL (≥ 2)] |
| RoxygenNote: | 6.0.1 |
| NeedsCompilation: | yes |
| Packaged: | 2025-03-17 12:25:40 UTC; edd |
| Author: | Dirk Eddelbuettel 
[aut, cre],
Romain Francois
[aut] |
| Maintainer: | Dirk Eddelbuettel <edd@debian.org> |
| Repository: | CRAN |
| Date/Publication: | 2025-03-17 12:40:08 UTC |
Examples for the Rcpp R/C++ Interface library
Description
This package shows some simple examples for the use of Rcpp.
It can also serve as a working template to create packages that use Rcpp to interface C++ code or libraries.
Details
The Rcpp package provides a number of C++ classes that ease access to C++ from R. This comprises both passing parameters to functions, as well as returning results back from C++ to R.
The RcppExamples package provides some simple examples for use of Rcpp. At this point the documentation is not complete in the sense of not covering all accessible classes. However, several basic use cases are illustrated,
Author(s)
Dominick Samperi wrote the initial versions of Rcpp (and RcppTemplate) during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008. Dirk Eddelbuettel and Romain Francois have been extending Rcpp since 2009.
See Also
The https://gallery.rcpp.org site regroups a number of examples.
Rcpp::DataFrame example for Rcpp
Description
A DataFrame can be passed C++ and can be instantiated as a
corresponding C++ object using the Rcpp API.
This example shows (in the corresponding C++ code) how to access, modify and create a data frame.
Details
Usage of Rcpp::DataFrame is fully defined in
the respective header file.
The C++ source file corresponding to the this function does the following:
// we receive a 'DF' data.frame object
// and access each column by name
Rcpp::IntegerVector a = DF["a"];
Rcpp::CharacterVector b = DF["b"];
Rcpp::DateVector c = DF["c"];
// do something
a[2] = 42;
b[1] = "foo";
c[0] = c[0] + 7; // move up a week
// create a new data frame
Rcpp::DataFrame NDF =
Rcpp::DataFrame::create(Rcpp::Named("a")=a,
Rcpp::Named("b")=b,
Rcpp::Named("c")=c);
// and return old and new in list
return(Rcpp::List::create(Rcpp::Named("origDataFrame")=DF,
Rcpp::Named("newDataFrame")=NDF));
Author(s)
Dirk Eddelbuettel and Romain Francois
Examples
## Not run:
RcppDataFrame()
## End(Not run)
C++ classes for interfacing date and datetime R objects
Description
Rcpp has the classes Rcpp::Date, Rcpp::Datetime,
Rcpp::DateVector and Rcpp::DatetimeVector.
Details
In the C++ code for the RcppDateExample.cpp file:
// [[Rcpp::export]]
List DateExample(DateVector & dv, DatetimeVector & dtv) {
Function formatDate("format.Date");
Function formatDatetime("format.POSIXct");
Rprintf("\nIn C++, seeing the following date value\n");
for (int i=0; i<dv.size(); i++) {
Rcout << as<std::string>(formatDate(wrap(dv[i]))) << std::endl;
dv[i] = dv[i] + 7; // shift a week
}
Rprintf("\nIn C++, seeing the following datetime value\n");
for (int i=0; i<dtv.size(); i++) {
Rcout << as<std::string>(formatDatetime(wrap(dtv[i]))) << std::endl;
dtv[i] = dtv[i] + 0.250; // shift 250 millisec
}
// Build result set to be returned as a list to R.
return List::create(Named("date", dv),
Named("datetime", dtv));
}
Author(s)
Dominick Samperi wrote the initial versions of Rcpp (and RcppTemplate) during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008. Dirk Eddelbuettel and Romain Francois have been extending Rcpp since 2009.
References
Writing R Extensions, available at https://www.r-project.org.
Examples
# set up date and datetime vectors
dvec <- Sys.Date() + -2:2
dtvec <- Sys.time() + (-2:2)*0.5
# call the underlying C++ function
result <- RcppDateExample(dvec, dtvec)
# inspect returned object
result
Examples of uses of List
Description
List is an Rcpp class that can be used to manipulate R lists.
Arguments
params |
A heterogeneous list specifying |
Value
RcppListExample returns a list containing:
method |
string input paramter |
tolerance |
double input paramter |
maxIter |
int input parameter |
startDate |
Date type with starting date |
params |
input parameter list (this is redundant because we returned the input parameters above) |
Author(s)
Dominick Samperi wrote the initial versions of Rcpp (and RcppTemplate) during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008. Dirk Eddelbuettel and Romain Francois have been extending Rcpp since 2009.
References
Writing R Extensions, available at https://www.r-project.org.
Examples
# set up some value
params <- list(method='BFGS',
tolerance=1.0e-5,
maxIter=100,
startDate=as.Date('2006-7-15'))
# call the underlying C++ function
result <- RcppListExample(params)
# inspect returned object
result
Example of using Rcpp NumericMatrix
Description
The NumericMatrix class represents numeric matrices
Details
The C++ code presented in the MatrixExample.cpp file:
#include <Rcpp.h>
#include <cmath>
// suncc needs help to disambiguate between sqrt( float ) and sqrt(double)
inline static double sqrt_double(double x) { return ::sqrt(x); }
using namespace Rcpp;
// [[Rcpp::export]]
List MatrixExample(const NumericMatrix & orig) {
NumericMatrix mat(orig.nrow(), orig.ncol());
// we could query size via
// int n = mat.nrow(), k=mat.ncol();
// and loop over the elements, but using the STL is so much nicer
// so we use a STL transform() algorithm on each element
std::transform(orig.begin(), orig.end(), mat.begin(), sqrt_double );
return List::create(Named("result") = mat,
Named("original") = orig);
}
Author(s)
Dominick Samperi wrote the initial versions of Rcpp (and RcppTemplate) during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008. Dirk Eddelbuettel and Romain Francois have been extending Rcpp since 2009.
References
Writing R Extensions, available at https://www.r-project.org.
Examples
M <- matrix((1:16)^2, 4)
RcppMatrixExample(M)
Rcpp NumericVector example
Description
Example on how to use a NumericVector and manipulate it with the STL.
Details
NumericVector orig ; // from R
NumericVector vec(orig.size()); // create a target vector of the same size
// we could query size via
// int n = vec.size();
// and loop over the vector, but using the STL is so much nicer
// so we use a STL transform() algorithm on each element
std::transform(orig.begin(), orig.end(), vec.begin(), sqrt_double );
return List::create(Named("result") = vec,
Named("original") = orig);
As shown in the example section, provided the seed is reset, the exact same draws can be obtained in R itself – which is important for reproducibility.
Author(s)
Dirk Eddelbuettel and Romain Francois
Examples
RcppNumericVectorExample(seq(1,9)^2)
Rcpp RNGs example
Description
Rcpp sugar provides numerous p/q/d/r functions for numerous distributions.
This example shows (in the corresponding C++ code) how to draw from three different distributions and returns a data frame.
Details
The various header file, and the Rcpp sugar vignette, provide full documentation for Rcpp sugar.
The C++ source file corresponding to the this function does the following:
int n; // length passed in from R
NumericVector rn = rnorm(n);
NumericVector rt = rt(n, 1.0);
NumericVector rp = rpois(n, 1.0);
// create a new data frame to return drawns
return DataFrame::create(Named("rnorm") = rn,
Named("rt") = rt,
Named("rpois") = rp);
As shown in the example section, provided the seed is reset, the exact same draws can be obtained in R itself – which is important for reproducibility.
Author(s)
Dirk Eddelbuettel and Romain Francois
Examples
set.seed(42)
X <- RcppRNGsExample(10L)
set.seed(42)
Y <- data.frame(rnorm=rnorm(10),rt=rt(10,1),rpois=rpois(10,1))
all.equal(X,Y)
Example of using Rcpp StringVector (aka CharacterVector)
Description
The StringVector (aka CharacterVector)
class represents character vectors.
Details
The C++ code presented in the StringVectorExample.cpp file:
#include <Rcpp.h>
using namespace Rcpp ;
// [[Rcpp::export]]
List StringVectorExample(const StringVector & orig) {
StringVector vec(orig.size());
std::transform(orig.begin(), orig.end(), vec.begin(),
make_string_transformer(tolower));
return List::create(Named("result") = vec,
Named("original") = orig);
}
Author(s)
Dominick Samperi wrote the initial versions of Rcpp (and RcppTemplate) during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008. Dirk Eddelbuettel and Romain Francois have been extending Rcpp since 2009.
References
Writing R Extensions, available at https://www.r-project.org.
Examples
RcppStringVectorExample(c("Tick", "Tack", "Tock"))
Convert Index and String Vector into CharacterVector, and vice versa
Description
These two functions are an illustration of how as.character and
as.factor may be reimplemented at the C++ level.
Usage
factor2char(iv)
char2factor(sv)
Arguments
iv |
A Integer Vector corresponding to numeric representation of the factor This vector is also expected to have an attribute ‘levels’ with the factor levels |
sv |
A String Vector |
Value
A Character Vector which at each position contains the level value of the corresponding index, or a Factor, depending on the function
Examples
f <- as.factor(c("red", "green", "blue", "red"))
factor2char(f);
f <- as.factor(c("red", "green", "blue", "red"))
v <- factor2char(f);
char2factor(v)