library package:base R Documentation _L_o_a_d_i_n_g _a_n_d _L_i_s_t_i_n_g _o_f _P_a_c_k_a_g_e_s _D_e_s_c_r_i_p_t_i_o_n: 'library' and 'require' load add-on packages. '.First.lib' is called when a package is loaded; '.Last.lib' is called when a package is detached. _U_s_a_g_e: library(package, help, pos = 2, lib.loc = NULL, character.only = FALSE, logical.return = FALSE, warn.conflicts = TRUE, keep.source = getOption("keep.source.pkgs"), verbose = getOption("verbose")) require(package, lib.loc = NULL, quietly = FALSE, warn.conflicts = TRUE, keep.source = getOption("keep.source.pkgs"), character.only = FALSE, save = TRUE) .First.lib(libname, pkgname) .Last.lib(libpath) _A_r_g_u_m_e_n_t_s: package, help: the name of a package, given as a name or literal character string, or a character string, depending on whether 'character.only' is 'FALSE' (default) or 'TRUE'). pos: the position on the search list at which to attach the loaded package. Note that '.First.lib' may attach other packages, and 'pos' is computed _after_ '.First.lib' has been run. Can also be the name of a position on the current search list as given by 'search()'. lib.loc: a character vector describing the location of R library trees to search through, or 'NULL'. The default value of 'NULL' corresponds to all libraries currently known. Non-existent library trees are silently ignored. character.only: a logical indicating whether 'package' or 'help' can be assumed to be character strings. logical.return: logical. If it is 'TRUE', 'FALSE' or 'TRUE' is returned to indicate success. warn.conflicts: logical. If 'TRUE', warnings are printed about 'conflicts' from attaching the new package, unless that package contains an object '.conflicts.OK'. A conflict is a function masking a function, or a non-function masking a non-function. keep.source: logical. If 'TRUE', functions 'keep their source' including comments, see argument 'keep.source' to 'options'. This applies only to the named package, and not to any packages or name spaces which might be loaded to satisfy dependencies or imports. This argument does not apply to packages using lazy-loading. Whether they have kept source is determined when they are installed (and is most likely false). verbose: a logical. If 'TRUE', additional diagnostics are printed. quietly: a logical. If 'TRUE', no message confirming package loading is printed. save: logical or environment. If 'TRUE', a call to 'require' from the source for a package will save the name of the required package in the variable '".required"', allowing function 'detach' to warn if a required package is detached. See section 'Packages that require other packages' below. libname: a character string giving the library directory where the package was found. pkgname: a character string giving the name of the package. libpath: a character string giving the complete path to the package. _D_e_t_a_i_l_s: 'library(package)' and 'require(package)' both load the package with name 'package'. 'require' is designed for use inside other functions; it returns 'FALSE' and gives a warning (rather than an error as 'library()' does by default) if the package does not exist. Both functions check and update the list of currently loaded packages and do not reload a package which is already loaded. (Furthermore, if the package has a name space and a name space of that name is already loaded, they work from the existing name space rather than reloading from the file system. If you want to reload a package, call 'detach' or 'unloadNamespace' first.) To suppress messages during the loading of packages use 'suppressPackageStartupMessages': this will suppress all messages from R itself but not necessarily all those from package authors. If 'library' is called with no 'package' or 'help' argument, it lists all available packages in the libraries specified by 'lib.loc', and returns the corresponding information in an object of class '"libraryIQR"'. The structure of this class may change in future versions. In earlier versions of R, only the names of all available packages were returned; use '.packages(all = TRUE)' for obtaining these. Note that 'installed.packages()' returns even more information. 'library(help = somename)' computes basic information about the package 'somename', and returns this in an object of class '"packageInfo"'. The structure of this class may change in future versions. When used with the default value ('NULL') for 'lib.loc', the loaded packages are searched before the libraries. '.First.lib' is called when a package without a name space is loaded by 'library'. (For packages with name spaces see '.onLoad'.) It is called with two arguments, the name of the library directory where the package was found (i.e., the corresponding element of 'lib.loc'), and the name of the package. It is a good place to put calls to 'library.dynam' which are needed when loading a package into this function (don't call 'library.dynam' directly, as this will not work if the package is not installed in a standard location). '.First.lib' is invoked after the search path interrogated by 'search()' has been updated, so 'as.environment(match("package:name", search()))' will return the environment in which the package is stored. If calling '.First.lib' gives an error the loading of the package is abandoned, and the package will be unavailable. Similarly, if the option '".First.lib"' has a list element with the package's name, this element is called in the same manner as '.First.lib' when the package is loaded. This mechanism allows the user to set package 'load hooks' in addition to startup code as provided by the package maintainers, but 'setHook' is preferred. '.Last.lib' is called when a package is detached. Beware that it might be called if '.First.lib' has failed, so it should be written defensively. (It is called within 'try', so errors will not stop the package being detached.) _V_a_l_u_e: Normally 'library' returns (invisibly) the list of loaded packages, but 'TRUE' or 'FALSE' if 'logical.return' is 'TRUE'. When called as 'library()' it returns an object of class '"libraryIQR"', and for 'library(help=)', one of class '"packageInfo"'. 'require' returns (invisbly) a logical indicating whether the required package is available. _P_a_c_k_a_g_e_s _t_h_a_t _r_e_q_u_i_r_e _o_t_h_e_r _p_a_c_k_a_g_e_s: *NB:* This mechanism has been almost entirely superseded by using the 'Depends:' field in the 'DESCRIPTION' file of a package. The source code for a package that requires one or more other packages should have a call to 'require', preferably near the beginning of the source, and of course before any code that uses functions, classes or methods from the other package. The default for argument 'save' will save the names of all required packages in the environment of the new package. The saved package names are used by 'detach' when a package is detached to warn if other packages still require the to-be-detached package. Also, if a package is installed with saved image (see INSTALL), the saved package names are used to require these packages when the new package is attached. _F_o_r_m_a_l _m_e_t_h_o_d_s: 'library' takes some further actions when package 'methods' is attached (as it is by default). Packages may define formal generic functions as well as re-defining functions in other packages (notably 'base') to be generic, and this information is cached whenever such a package is loaded after 'methods' and re-defined functions (implicit generics) are excluded from the list of conflicts. The caching and check for conflicts require looking for a pattern of objects; the search may be avoided by defining an object '.noGenerics' (with any value) in the package. Naturally, if the package _does_ have any such methods, this will prevent them from being used. _N_o_t_e: 'library' and 'require' can only load an _installed_ package, and this is detected by having a 'DESCRIPTION' file containing a 'Built:' field. Under Unix-alikes, the code checks that the package was installed under a similar operating system as given by 'R.version$platform' (the canonical name of the platform under which R was compiled), provided it contains compiled code. Packages which do not contain compiled code can be shared between Unix-alikes, but not to other OSes because of potential problems with line endings and OS-specific help files. If sub-architectures are used, the OS similarity is not checked since the OS used to build may differ (e.g. 'i386-pc-linux-gnu' code can be built on an 'x86_64-unknown-linux-gnu' OS). The package name given to 'library' and 'require' must match the name given in the package's 'DESCRIPTION' file exactly, even on case-insensitive file systems such as MS Windows. _R_e_f_e_r_e_n_c_e_s: Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S Language_. Wadsworth & Brooks/Cole. _S_e_e _A_l_s_o: '.libPaths', '.packages'. 'attach', 'detach', 'search', 'objects', 'autoload', 'library.dynam', 'data', 'install.packages' and 'installed.packages'; 'INSTALL', 'REMOVE'. _E_x_a_m_p_l_e_s: library() # list all available packages library(lib.loc = .Library) # list all packages in the default library library(help = splines) # documentation on package 'splines' library(splines) # load package 'splines' require(splines) # the same search() # "splines", too detach("package:splines") # if the package name is in a character vector, use pkg <- "splines" library(pkg, character.only = TRUE) detach(pos = match(paste("package", pkg, sep=":"), search())) require(pkg, character.only = TRUE) detach(pos = match(paste("package", pkg, sep=":"), search())) require(nonexistent) # FALSE ## Not run: ## Suppose a package needs to call a DLL named 'fooEXT', ## where 'EXT' is the system-specific extension. Then you should use .First.lib <- function(lib, pkg) library.dynam("foo", pkg, lib) ## if you want to mask as little as possible, use library(mypkg, pos = "package:base") ## End(Not run)