installed.packages(utils)
installed.packages()所属R语言包：utils
Find Installed Packages
查找已安装的软件包
译者：生物统计家园网 机器人LoveR
描述----------Description----------
Find (or retrieve) details of all packages installed in the specified libraries.
查找（或检索）在指定库中安装的所有软件包的详细信息。
用法----------Usage----------
installed.packages(lib.loc = NULL, priority = NULL,
noCache = FALSE, fields = NULL,
subarch = .Platform$r_arch)
参数----------Arguments----------
参数：lib.loc
character vector describing the location of R library trees to search through, or NULL for all known trees (see .libPaths).
特征向量描述R库树木的位置进行搜索，或NULL所有已知的树木（见.libPaths）。
参数：priority
character vector or NULL (default). If non-null, used to select packages; "high" is equivalent to c("base", "recommended"). To select all packages without an assigned priority use priority = "NA".
特征向量或NULL（默认）。如果非空，用于选择包; "high"相当于c("base", "recommended")的。要选择所有的包，没有分配的优先使用priority = "NA"。
参数：noCache
Do not use cached information, nor cache it.
不使用缓存的信息，也没有缓存。
参数：fields
a character vector giving the fields to extract from each package's DESCRIPTION file in addition to the default ones, or NULL (default). Unavailable fields result in NA values.
领域的一个字符向量，提取每个包的DESCRIPTION文件中除了默认的，或者NULL（默认）。 NA值不可用领域的结果。
参数：subarch
character string or NULL. If non-null and non-empty, used to select packages which are installed for that sub-architecture.
字符串或NULL。如果非空非空，用来选择安装的软件包，子结构。
Details
详情----------Details----------
installed.packages scans the "DESCRIPTION" files of each package found along lib.loc and returns a matrix of package names, library paths and version numbers.
installed.packages扫描DESCRIPTION发现每包沿lib.loc返回的包名，库的路径和版本号的矩阵文件。
The information found is cached (by library) for the R session and specified fields argument, and updated only if the top-level library directory has been altered, for example by installing or removing a package. If the cached information becomes confused, it can be refreshed by running installed.packages(noCache = TRUE).
信息发现是缓存（库）的R会话，并指定fields参数，更新，只有顶级的图书馆目录已经改变，例如安装或删除包。如果缓存信息变得混乱，它可以刷新运行installed.packages(noCache = TRUE)。
值----------Value----------
A matrix with one row per package, row names the package names and column names (currently) "Package", "LibPath", "Version", "Priority", "Depends", "Imports", "LinkingTo", "Suggests", "Enhances", "OS_type", "License" and "Built" (the R version the package was built under). Additional columns can be specified using the fields argument.
矩阵与每一个行包，行名包名和列名（目前）"Package"，"LibPath"，"Version"，"Priority"，"Depends"， "Imports"，"LinkingTo"，"Suggests"，"Enhances"，"OS_type"，"License"和"Built"（R版本的包建下） 。使用fields参数，可以指定额外的列。
注意----------Note----------
This can be slow when thousands of packages are installed, so do not use this to find out if a named package is installed (use system.file or find.package from package base) nor to find details of a small number of packages (use packageDescription). It needs to read several files per installed package, which will be slow on Windows and on some network-mounted file systems.
这可能会很慢时，安装数以千计的包，所以不使用此找出一个名为包安装（使用system.file或find.package包base）也找到细节一个小的包数（使用packageDescription）。它需要读取多个文件，每安装的软件包，这将是在Windows和一些网络安装的文件系统的缓慢。
参见----------See Also----------
update.packages, install.packages, INSTALL, REMOVE.
update.packages，install.packages，INSTALL，REMOVE。
举例----------Examples----------
str(ip <- installed.packages(priority = "high"))
ip[, c(1,3:5)]
plic <- installed.packages(priority = "high", fields="License")
## what licenses are there:[＃什么牌有：]
table( plic[,"License"] )
转载请注明:出自 生物统计家园网(http://www.biostatistic.net)。
注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
注2：由于是机器人自动翻译，难免有不准确之处，使用时仔细对照中、英文内容进行反复理解，可以帮助R语言的学习。
注3：如遇到不准确之处，请在本贴的后面进行回帖，我们会逐渐进行修订。
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发表于 2012-2-16 21:06:48
