{"id":22628,"date":"2023-02-28T02:06:11","date_gmt":"2023-02-28T02:06:11","guid":{"rendered":"https:\/\/www.booksofall.com\/es\/?post_type=product&p=22628"},"modified":"2023-02-28T02:06:12","modified_gmt":"2023-02-28T02:06:12","slug":"writing-r-extensions","status":"publish","type":"product","link":"https:\/\/www.booksofall.com\/es\/writing-r-extensions\/","title":{"rendered":"Writing R Extensions"},"content":{"rendered":"

Packages provide a mechanism for loading optional code<\/a>, data and documentation as needed. The R<\/a> distribution itself includes about 30 packages.<\/p>\n

In the following, we assume that you know the library() command, including its lib.loc argument, and we also assume basic knowledge of the R CMD INSTALL utility. Otherwise, please look at R\u2019s help pages on<\/p>\n

?library<\/p>\n

?INSTALL<\/p>\n

before reading on.<\/p>\n

For packages which contain code to be compiled, a computing environment including a number of tools is assumed; the \u201cR Installation and Administration<\/a>\u201d manual describes what is needed for each OS.<\/p>\n

Once a source package is created, it must be installed by the command R CMD INSTALL. See Section \u201cAdd-on-packages\u201d in R Installation and Administration.<\/p>\n

Other types of extensions are supported (but rare): See Section 1.10 [Package types], page 75.<\/p>\n

Some notes on terminology complete this introduction. These will help with the reading of this manual, and also in describing concepts accurately when asking for help.<\/p>\n

A package is a directory of files which extend R, a source package (the master files of a package), or a tarball containing the files of a source package, or an installed package, the result of running R CMD INSTALL<\/a> on a source package. On some platforms (notably macOS and Windows) there are also binary packages, a zip file or tarball containing the files of an installed package which can be unpacked rather than installing from sources.<\/p>\n

A package is not1 a library. The latter is used in two senses in R documentation.<\/p>\n

\u2022 A directory into which packages are installed, e.g. \/usr\/lib\/R\/library: in that sense it is sometimes referred to as a library directory or library tree (since the library is a directory which contains packages as directories, which themselves contain directories).<\/p>\n

\u2022 That used by the operating system, as a shared, dynamic or static library or (especially on Windows) a DLL<\/a>, where the second L<\/a> stands for \u2018library\u2019. Installed packages may contain compiled code in what is known on Unix-alikes<\/a> as a shared object and on Windows as a DLL. The concept of a shared library (dynamic library on macOS) as a collection of compiled code to which a package might link is also used, especially for R itself on some platforms. On most platforms these concepts are interchangeable (shared objects and DLLs can both be loaded into the R process and be linked against), but macOS distinguishes between shared objects (extension .so) and dynamic libraries (extension .dylib).<\/p>\n

There are a number of well-defined operations on source packages.<\/p>\n

\u2022 The most common is installation which takes a source package and installs it in a library using R CMD INSTALL or install.packages.<\/p>\n

\u2022 Source packages can be built. This involves taking a source directory and creating a tarball ready for distribution, including cleaning it up and creating PDF documentation from any vignettes it may contain. Source packages (and most often tarballs) can be checked, when a test installation is done and tested (including running its examples); also, the contents of the package are tested in various ways for consistency and portability.<\/p>\n

\u2022 Compilation is not a correct term for a package. Installing a source package which contains C, C++ or Fortran code will involve compiling that code. There is also the possibility of \u2018byte\u2019 compiling the R code in a package (using the facilities of package compiler): nowadays<\/p>\n

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