刚刚介绍了如何调用C，那么C++可以吗？R本来是只认C代码的，当然如果你使用C++代码编译也可以通过，但是R却无法调用它。
如果想在R中调用C++代码，那就必须使用Rcpp。使用Rcpp非常简单。
首先我们还是来一个hello qiuworld吧。
首先看一眼目录结构。
·- mypackage |- DESCRIPTION |- NAMESPACE ·- R | |- rcpp_hello_world.R ·- man | |- mypackage-package.Rd |- rcpp_hello_world.Rd ·- src |- Makevars |- Makevars.win |- rcpp_hello_world.cpp |- rcpp_hello_world.h |
在rcpp_hello_world.R中写入
rcpp_hello_world <- function(){
.Call( "rcpp_hello_world", PACKAGE = "mypackage" )
} |
在rcpp_hello_world.h中写入
#ifndef RCPP_HELLO_WORLD_H_H #define RCPP_HELLO_WORLD_H_H #include <Rcpp.h> RcppExport SEXP rcpp_hello_world() ; #endif |
在
rcpp_hello_world.cpp中写入
#include "rcpp_hello_world.h" SEXP rcpp_hello_world(){ using namespace Rcpp ; CharacterVector x = CharacterVector::create( "hello", "qiuworld" ) ; NumericVector y = NumericVector::create( 0.0, 1.0 ) ; List z = List::create( x, y ) ; return z ; } |
在DESCRIPTION文件中写入
Package: helloCpp Type: Package Title: What the package does (short line) Version: 1.0 Date: 2012-06-28 Author: Who wrote it Maintainer: Who to complain to <yourfault@somewhere.net> Description: More about what it does (maybe more than one line) License: What Licence is it under ? Depends: Rcpp (>= 0.9.13) LinkingTo: Rcpp |
在NAMESPACE文件中写入
useDynLib(helloCpp)
exportPattern("^[[:alpha:]]+") |
在Makevars中写入
## Use the R HOME indirection to support installations of multiple R version PKG_LIBS = `$(R_HOME)/bin/Rscript -e "Rcpp:::LdFlags()"` |
在Makevars.win中写入
## Use the R HOME indirection to support installations of multiple R version
PKG_LIBS = $(shell "${R_HOME}/bin${R_ARCH_BIN}/Rscript.exe" -e "Rcpp:::LdFlags()") |
在helloCpp.Rd中写入
\name{helloCpp-package}
\alias{helloCpp-package}
\alias{helloCpp}
\docType{package}
\title{
What the package does (short line)
}
\description{
More about what it does (maybe more than one line)
~~A concise (1-5 lines) description of the package~~
}
\details{
\tabular{ll}{
Package: \tab helloCpp\cr
Type: \tab Package\cr
Version: \tab 1.0\cr
Date: \tab 2012-06-28\cr
License: \tab What license is it under?\cr
}
~~An overview of how to use the package, including the most important~~
~~functions~~
}
\author{
Who wrote it
Maintainer: Who to complain to <yourfault@somewhere.net>
}
\references{
~~Literature or other references for background information~~
}
~~Optionally other standard keywords, one per line, from file KEYWORDS in~~
~~the R documentation directory~~
\keyword{ package }
\seealso{
~~Optional links to other man pages, e.g.~~
~~\code{\link[<pkg>:<pkg>-package]{<pkg>}}~~
}
\examples{
%%~~simple examples of the most important functions~~
} |
在rcpp_hello_world.Rd中写入
\name{rcpp_hello_world}
\alias{rcpp_hello_world}
\docType{package}
\title{
Simple function using Rcpp
}
\description{
Simple function using Rcpp
}
\usage{
rcpp_hello_world()
}
\examples{
\dontrun{
rcpp_hello_world()
}
} |
然后在terminal当前目录下运行，
R CMD check mypackage R CMD build mypackage R CMD INSTALL mypackage_1.0.tar.gz |
而后就可以在R当中运行
> library(mypackage) > rcpp_hello_world() [[1]] [1] "hello" "qiuworld" [[2]] [1] 0 1 |
一切OK.
