,
Romain Francois [aut] ,
Dominick Samperi [aut] (Initial code during 2005-2006)| Title: | Examples using 'RcppClassic' to Interface R and C++ |
|---|---|
| Description: | The 'Rcpp' package contains a C++ library that facilitates the integration of R and C++ in various ways via a rich API. This API was preceded by an earlier version which has been deprecated since 2010 (but is still supported to provide backwards compatibility in the package 'RcppClassic'). This package 'RcppClassicExamples' provides usage examples for the older, deprecated API. There is also a corresponding package 'RcppExamples' with examples for the newer, current API which we strongly recommend as the basis for all new development. |
| Authors: | Dirk Eddelbuettel [aut, cre] ,
Romain Francois [aut] ,
Dominick Samperi [aut] (Initial code during 2005-2006) |
| Maintainer: | Dirk Eddelbuettel <[email protected]> |
| License: | GPL (>= 2) |
| Version: | 0.1.3 |
| Built: | 2024-12-15 05:15:56 UTC |
| Source: | https://github.com/eddelbuettel/rcppclassicexamples |
This package shows some simple examples for the use of the deprecated classic API from the first implementation of Rcpp.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
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.
Two APIs are supported. The first is an older API which was first introduced mostly in 2006 and extended in 2008. This interface is used by a few other packages and will be supported going forward in the RcppClassic-package package.
A second and newer API that was started in 2009 offers more functionality, see the Rcpp-package package.
The RcppExamples package provides some simple examples for use of Rcpp.
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 the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
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.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
Usage of Rcpp::DataFrame is fully defined in
the respective header file.
The C++ source file corresponding to the this function does the
following (inside of a try/catch block):
// construct the data.frame object
Rcpp::DataFrame DF = Rcpp::DataFrame(Dsexp);
// 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));
Dirk Eddelbuettel and Romain Francois
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
## Not run: RcppDataFrame() ## End(Not run)## Not run: RcppDataFrame() ## End(Not run)
RcppDate, RcppDatetime, RcppDateVector and
RcppDatetimeVector are C++ classes defined in their respective
headers files. They are part of the 'classic' Rcpp API. These classes
pass scalars and vectors of R objects of types Date and
POSIXct, respectively, to C++ via the .Call() function
interface.
Member functions are provided to query the dimension of the vector or
matrix object, convert it in a corresponding C representation.
R objects of type Date, and hence the RcppDate and
RcppDateVector objects, are internally represented as an
integer counting days since the epoch, i.e. January 1,
1970. Similarly, R objects of type POSIXct and the
RcppDatetime and RcppDatetimeVector objects, are
internally represented as seconds since the epoch. However, R
extends the POSIX standard by using a double leading to microsecond
precision in timestamps. This is fully supported by Rcpp as
well.
The new API currently has the classes Rcpp::Date, Rcpp::Datetime,
Rcpp::DateVector and Rcpp::DatetimeVector which are preferred
for new developments, as is the rest of the new API in the Rcpp package
while the RcppClassic package has been deprecated since
2010.
Usage of the RcppDate, RcppDatetime (and their vector
extensions) in C++ is fully defined in the respective header
files RcppDate.h and RcppDatetime.h.
As example, consider a call from R to C++ such as
# an R example passing one type of each class to a function
# someFunction in package somePackage
val <- .Call("someFunction",
Sys.Date(), # current date
Sys.time(), # current timestamp
as.Date("2000-02-25")
+ 0:5, # date vector
ISOdatetime(1999,12,31,23,59,0)
+ (0:5)*0.250, # datetime vector
PACKAGE="somePackage")
At the C++ level, the corresponding code to assign these parameter to
C++ objects is can be as follows::
SEXP someFunction(SEXP ds, SEXP dts,
SEXP dvs, SEXP dtvs) {
RcppDate d(ds);
RcppDatetime dt(dts);
RcppDateVector dv(dvs);
RcppDatetimeVector dtv(dtvs);
}
Standard accessor functions are defined, see RcppDate.h and
RcppDatetime.h for details.
Objects of these types can also be returned via RcppResultSet.
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.
Writing R Extensions, available at https://www.r-project.org.
RcppResultSet.
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
# 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# 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
RcppExample illustrates how the older Rcpp R/C++
interface class library is used. It provides fairly complete coverage
for the older ‘classic’ API.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec, fnvec, fnlist) ## S3 method for class 'RcppExample' print(x,...)RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec, fnvec, fnlist) ## S3 method for class 'RcppExample' print(x,...)
params |
A heterogeneous list specifying |
nlist |
a list of named numeric values (double or int). |
numvec |
a numeric 1D vector (double or int). |
nummat |
a numeric 2D matrix (double or int). |
df |
a data frame. |
datevec |
a vector of Date's. |
stringvec |
a vector of strings. |
fnvec |
an R function with numeric vector argument. |
fnlist |
an R function with list argument. |
x |
Object of type |
... |
Extra named parameters. |
The C++ represention of data frames are not passed back to R in a form
that R recognizes as a data frame, but it is a simple matter to do the
conversion. For example, the return value named PreDF (see
return values below) is not seen as a data frame on the R side (thus
the name "pre-data frame"), but it can be converted to a data frame
using df <- data.frame(result$PreDF).
The print.RcppExample() function is defined so that we can control what gets printed when a variable assigned the return value is entered on a line by itself. It is defined to simply list the names of the fields returned (see RcppExample.R).
RcppExample returns a list containing:
method |
string input paramter |
tolerance |
double input paramter |
maxIter |
int input parameter |
nlFirstName |
first name in nlist |
nlFirstValue |
first value in nlist |
matD |
R matrix from an RcppMatrix<double> object |
stlvec |
R vector from a vector<double> object |
stlmat |
R matrix from a vector<vector<double> > object |
a |
R matrix from C/C++ matrix |
v |
R vector from C/C++ vector |
strings |
R vector of strings from vector<string> object |
InputDF |
a data frame passed in from R |
PreDF |
a data frame created on C++ side to be passed back to R |
params |
input parameter list (this is redundant because we returned the input parameters above) |
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.
Writing R Extensions, available at https://www.r-project.org.
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
params <- list(method='BFGS', tolerance=1.0e-8, maxIter=1000, startDate=as.Date('2006-7-15')) nlist <- list(ibm = 80.50, hp = 53.64, c = 45.41) numvec <- seq(1,5) # numerical vector nummat <- matrix(seq(1,20),4,5) # numerical matrix stringvec <- c("hello", "world", "fractal") # string vector datestr <- c('2006-6-10', '2006-7-12', '2006-8-10') datevec <- as.Date(datestr, "%Y-%m-%d") # date vector df <- data.frame(a=c(TRUE, TRUE, FALSE), b=I(c('a','b','c')), c=c('beta', 'beta', 'gamma'), dates=datevec) fnvec <- function(x) { sum(x) } # Add up components of vector fnlist <- function(l) { # Return vector with 1 added to each component vec <- c(l$alpha + 1, l$beta + 1, l$gamma + 1) vec } result <- RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec, fnvec, fnlist) resultparams <- list(method='BFGS', tolerance=1.0e-8, maxIter=1000, startDate=as.Date('2006-7-15')) nlist <- list(ibm = 80.50, hp = 53.64, c = 45.41) numvec <- seq(1,5) # numerical vector nummat <- matrix(seq(1,20),4,5) # numerical matrix stringvec <- c("hello", "world", "fractal") # string vector datestr <- c('2006-6-10', '2006-7-12', '2006-8-10') datevec <- as.Date(datestr, "%Y-%m-%d") # date vector df <- data.frame(a=c(TRUE, TRUE, FALSE), b=I(c('a','b','c')), c=c('beta', 'beta', 'gamma'), dates=datevec) fnvec <- function(x) { sum(x) } # Add up components of vector fnlist <- function(l) { # Return vector with 1 added to each component vec <- c(l$alpha + 1, l$beta + 1, l$gamma + 1) vec } result <- RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec, fnvec, fnlist) result
RcppParams is a C++ class defined in Rcpp.h that receive
any number of scalar parameters of types in a single named list object
from R through the .Call() function.
The parameters can be of different types that are limited to the R
types numeric, integer, character, logical
or Date. These types are mapped into, respectively, the
corresponding C++ types double, int, string,
bool and Date (a custom class defined by Rcpp.
RcppParams is part of the old deprecated Rcpp API, and should
be replaces by Rcpp::List which is more flexible and can be
used for both inputs and outputs. RcppParams is retained for
backwards compatibility, but should be avoided in new projects and
replaced in old projects.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
params |
A heterogeneous list specifying |
Usage of RcppParams from R via .Call() is as follows:
# an R example passing one type of each class to a function
# someFunction in package somePackage
val <- .Call("someFunction",
list(pie=3.1415, magicanswer=42, sometext="foo",
yesno=true, today=Sys.date()),
PACKAGE="somePackage")
At the C++ level, the corresponding code to assign these parameter to C++ objects is
SEXP someFunction(SEXP params) {
RcppParams par(params);
double p = par.getDoubleValue("pie");
int magic = par.getIntValue("magicanswer");
string txt = par.getStringValue("sometext");
bool yn = par.getBoolValue("yesno");
RcppDate d = par.getDateValue("today");
// some calculations ...
// some return values ...
}
As the lookup is driven by the names givem at the R level, order is not important. It is however important that the types match. Errors are typically caught and an exception is thrown.
The class member function checkNames can be used to verify that the
SEXP object passed to the function contains a given set of
named object.
RcppExample 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) |
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.
Writing R Extensions, available at https://www.r-project.org.
RcppExample.
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
# 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 <- RcppParamsExample(params) # inspect returned object result# 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 <- RcppParamsExample(params) # inspect returned object result
RcppResultSet is a C++ class defined in RcppResultSet.h that can
assign any number of C++ objects to R in a single named list object
as the SEXP return value of a .Call() function call. It
is part of the classic API.
The C++ objects can be of different types that are limited to
types double, int, string, vectors of
double or int (with explicit dimensions),
matrices of double or int (with explicit dimensions),
STL vectors of double, int or string, STL
‘vector of vectors’ of types double or int (all
with implicit dimensions), the internal types RcppDate, RcppDateVector,
RcppStringVector, RcppVector of types double or
int, RcppMatrix of types double or int
as well RcppFrame, a type that can be converted into a
data.frame, and the R type SEXP.
Where applicable, the C++ types are automatically converted to the
corresponding R types structures around types numeric,
integer, or character. The C++ code can all be
retrieved in R as elements of a named list object.
The new API has more generic templated functions.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
Usage of RcppResultSet from C++ is fully defined in
RcppResultSet.h. An example for returning data to R at the end of a
.Call() call follows.
At the C++ level, the corresponding code to assign these parameter to
C++ objects is can be as follows (taken from the C++ source of
RcppExample):
SEXP rl;
RcppResultSet rs;
rs.add("date", aDate); // RcppDate
rs.add("dateVec", dateVec); // RcppDateVec
rs.add("method", method); // string
rs.add("tolerance", tol); // numeric
rs.add("maxIter", maxIter); // int
rs.add("matD", matD); // RcppMatrix
rs.add("stlvec", stlvec); // vector<double> or <int>
rs.add("stlmat", stlmat); // vector< vector <double> >
// or <int>
rs.add("a", a, nrows, ncols); // double** (or int**) with
// two dimension
rs.add("v", v, len); // double* (or int*) with
// one dimension
rs.add("stringVec", strVec); // RcppStringVector
rs.add("strings", svec); // vector<string>
rs.add("InputDF", inframe); // RcppFrame
rs.add("PreDF", frame); // RcppFrame
rl = rs.getReturnList();
return(rl);
As the R level, we assign the returned object a list variables from which we select each list element by its name. lookup is driven by the names givem at the R level, order is not important. It is however important that the types match. Errors are typically caught and an exception is thrown.
The class member function checkNames can be used to verify that the
SEXP object passed to the function contains a given set of
named object.
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.
RcppExample.
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
# example from RcppDate # 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# example from RcppDate # 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
RcppVector, RcppMatrix and RcppStringVector are
C++ classes that can pass vectors (matrices) of R objects of
appropriate types to C++ via the .Call() function interface.
They are part of the 'classic' Rcpp API.
The vector and matrix types are templated and can operate on R types
intger and numeric.
The RcppVectorView and RcppMatrixView are slighly more
lightweight read-only variants.
Member functions are provided to query the dimension of the vector or
matrix object, convert it in a corresponding C representation,
and also to convert it into a corresponding STL object.
The new API has classes NumericVector, NumericMatrix,
CharacterVector (and also an alias StringVector).
The files RcppVectorExample.cpp and
RcppMatrixExample.cpp provide examples for both the classic and
new APIs.
Note that the RcppClassic package has been deprecated since 2010, all new development should use the Rcpp package instead.
Usage of RcppVector, RcppMatrix and
RcppStringVector in C++ is fully defined in
the respective header files.
As example, consider a call from R to C++ such as
# an R example passing one type of each class to a function
# someFunction in package somePackage
val <- .Call("someFunction",
rnorm(100), # numeric vector
sample(1:10, 5, TRUE) # int vector
search(), # character vector
as.matrix(rnorm(100),10,10), # matrix
PACKAGE="somePackage")
At the C++ level, the corresponding code to assign these parameter to
C++ objects is can be as follows (taken from the C++ source of
RcppExample):
SEXP someFunction(SEXP nvec, SEXP ivec,
SEXP svec, SEXP nmat) {
RcppVector<double> nv(nvec);
RcppVector<int> iv(ivec);
RcppStringVector sv(svec);
RcppMatrix<double> nm(nmat);
}
These C++ objects could then be queried via
int n = nv.size();
int d1 = nm.dim1(), d2 = nm.dim2();
to retrieve, respectively, vector length and matrix dimensions.
Moreover, the stlVector() and stlMatrix() member
functions can be used to convert the objects into STL objects:
vector<int> ivstl = iv.stlVector();
vector< vector< double > > = nm.stlMatrix();
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.
RcppExample.
See the RcppExamples-package for examples of the recommended Rcpp API and Rcpp-package for documentation on the recommended API to extend R with C++ code, while the deprecated RcppClassic-package documents the older, deprecated API.
# set up some value vector <- (seq(1,9))^2 # call the underlying C++ function result <- RcppVectorExample(vector) # inspect returned object result# set up some value vector <- (seq(1,9))^2 # call the underlying C++ function result <- RcppVectorExample(vector) # inspect returned object result