r - 从同一包中的 R 代码调用 Rcpp c++​​ 函数

Question

我想用 C++ 和 R 代码构建一个 Rcpp 包。仅使用 C++ 代码(删除了 R 代码)，所有内容都可以编译并运行良好，并且在构建和加载导出函数后可以按预期调用

<packageName>::<functionName>()

但是，当包含 R 代码和对 C++ 代码的调用时，我在构建包时遇到找不到对象的错误:

R CMD build <packageName>
[...]
** R
** byte-compile and prepare package for lazy loading
Error in <functionName>() :
  object '_<packageName>_<functionName>' not found
Error: unable to load R code in package '<packageName>'

错误发生在C++代码编译成功后。

<functionName>()

映射到

_<packageName>_<functionName>

像往常一样在 R/RcppExports.R 中，但它似乎不能在构建时由 R 代码加载。

包的结构和往常一样:

<packageName>
├── DESCRIPTION
├── man
│   ├── <functionName>.rd
│   └── <packageName>-package.rd
├── NAMESPACE
├── R
│   ├── <RCodeFileName>.R
│   └── RcppExports.R   
├── README.md
└── src
    ├── <C++CodeFileName>.cpp
    ├── <C++CodeFileName>.o
    ├── <packageName>.so
    ├── RCppExports.cpp
    ├── RCppExports.o
    └── symbols.rds

编译包时生成.o和.so文件的地方。

R文件直接调用C++文件中的函数:

[other stuff]
[...]
<functionName>()

NAMESPACE 文件也照常:

useDynLib(<packageName>, .registration=TRUE)
importFrom(Rcpp, evalCpp)
exportPattern("^[[:alpha:]]+")

这似乎是一个非常简单直接的问题(从 Rcpp 包中的 R 代码调用 C++ 代码)。尽管如此，我似乎无法找到任何说明应该如何完成的指示。

编辑(2020 年 4 月 8 日):build 与 INSTALL

在每种情况下都会出现这个问题

R CMD INSTALL <packageName>_<version>.tar.gz

如果包含帮助文件

man/<packageName>-package.Rd

被构建以便它强制安装包来处理帮助页面错误已经发生在

R CMD build <packageName>

如上所述。

编辑(2020 年 4 月 8 日):使用 Rcpp.package.skeleton() 重现的步骤(无论如何在类 Unix 系统上)

Rscript -e 'Rcpp::Rcpp.package.skeleton("demo20200408")'
echo 'rcpp_hello_world()' > errorDemo/R/example.R
R CMD INSTALL errorDemo

Answer 1

你可能想放慢速度。 Rcpp 包本身通过Rcpp.package.skeleton() 函数附带了一个演示包生成器。运行它!

逐个比较您所拥有的。

第二个生成器例如内置于 RStudio 中，可在文件 -> 新建项目 -> 新建目录 -> Package with Rcpp 菜单选项下使用。

否则，很难说。你对你的函数名做了什么奇怪的事吗？因为它们被映射到 R 和 C++，所以您受到两者的限制。 即您不能使用点(因为那将是 C++ 中的类方法表示法)。

最后，即使未导出，C++ 函数也应该可以通过三个冒号从安装和加载的包中获得，即 mypkg:::myFun().

最后，快速演示:

创建它

edd@rob:/tmp$ Rscript -e 'Rcpp::Rcpp.package.skeleton("demo20200408")'
Creating directories ...
Creating DESCRIPTION ...
Creating NAMESPACE ...
Creating Read-and-delete-me ...
Saving functions and data ...
Making help files ...
Done.
Further steps are described in './demo20200408/Read-and-delete-me'.

Adding Rcpp settings
 >> added Imports: Rcpp
 >> added LinkingTo: Rcpp
 >> added useDynLib directive to NAMESPACE
 >> added importFrom(Rcpp, evalCpp) directive to NAMESPACE
 >> added example src file using Rcpp attributes
 >> added Rd file for rcpp_hello_world
 >> compiled Rcpp attributes 
edd@rob:/tmp$ 

安装

edd@rob:/tmp$ R CMD INSTALL demo20200408 
* installing to library ‘/usr/local/lib/R/site-library’
* installing *source* package ‘demo20200408’ ...
** using staged installation
** libs
ccache g++ -I"/usr/share/R/include" -DNDEBUG  -I"/usr/local/lib/R/site-library/Rcpp/include"   -fpic  -g -O3 -Wall -pipe -pedantic  -c RcppExports.cpp -o RcppExports.o
ccache g++ -I"/usr/share/R/include" -DNDEBUG  -I"/usr/local/lib/R/site-library/Rcpp/include"   -fpic  -g -O3 -Wall -pipe -pedantic  -c rcpp_hello_world.cpp -o rcpp_hello_world.o
ccache g++ -Wl,-S -shared -L/usr/lib/R/lib -Wl,-Bsymbolic-functions -Wl,-z,relro -o demo20200408.so RcppExports.o rcpp_hello_world.o -L/usr/lib/R/lib -lR
installing to /usr/local/lib/R/site-library/00LOCK-demo20200408/00new/demo20200408/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded from temporary location
** checking absolute paths in shared objects and dynamic libraries
** testing if installed package can be loaded from final location
** testing if installed package keeps a record of temporary installation path
* DONE (demo20200408)
edd@rob:/tmp$ 

运行它

edd@rob:/tmp$ Rscript -e 'library(demo20200408); rcpp_hello_world()'
[[1]]
[1] "foo" "bar"

[[2]]
[1] 0 1

edd@rob:/tmp$ 

并添加一个 R 函数并调用它

edd@rob:/tmp$ echo 'r_hello_world <- function() cat("hi there\n")' > demo20200408/R/foo.R
edd@rob:/tmp$ R CMD INSTALL demo20200408 
* installing to library ‘/usr/local/lib/R/site-library’
* installing *source* package ‘demo20200408’ ...
** using staged installation
** libs
make: Nothing to be done for 'all'.
installing to /usr/local/lib/R/site-library/00LOCK-demo20200408/00new/demo20200408/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded from temporary location
** checking absolute paths in shared objects and dynamic libraries
** testing if installed package can be loaded from final location
** testing if installed package keeps a record of temporary installation path
* DONE (demo20200408)
edd@rob:/tmp$ Rscript -e 'library(demo20200408); r_hello_world()'
hi there
edd@rob:/tmp$ 

尽管 OP 声称仍然没有问题

在下面的最新评论中声称无法调用生成的函数。那是错误的。

edd@rob:/tmp$ editor demo20200408/R/foo.R    # subst. fave editor here
edd@rob:/tmp$ cat demo20200408/R/foo.R 
r_hello_world <- function() {
        cat("hi there\n")
        ignored <- rcpp_hello_world()
        NULL
}
edd@rob:/tmp$ R CMD INSTALL demo20200408 
* installing to library ‘/usr/local/lib/R/site-library’
* installing *source* package ‘demo20200408’ ...
** using staged installation
** libs
make: Nothing to be done for 'all'.
installing to /usr/local/lib/R/site-library/00LOCK-demo20200408/00new/demo20200408/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded from temporary location
** checking absolute paths in shared objects and dynamic libraries
** testing if installed package can be loaded from final location
** testing if installed package keeps a record of temporary installation path
* DONE (demo20200408)
edd@rob:/tmp$ Rscript -e 'library(demo20200408); r_hello_world()'
hi there
NULL
edd@rob:/tmp$