R help

学习R最重要的, 其实也是学习任何语言都可能是最重要的.

在线帮助, 和一些小技巧.

使用ls()函数可以查看当前环境中的对象

> a <- 1:10
> a
 [1]  1  2  3  4  5  6  7  8  9 10
> ls()
[1] "a"
> b <- 10:19
> c <- data.frame(a,b)
> ls()
[1] "a" "b" "c"

使用ls.str()可以查看当前环境中对象的详细信息.

> ls.str()
a :  int [1:10] 1 2 3 4 5 6 7 8 9 10
b :  int [1:10] 10 11 12 13 14 15 16 17 18 19
c : 'data.frame':       10 obs. of  2 variables:
 $ a: int  1 2 3 4 5 6 7 8 9 10
 $ b: int  10 11 12 13 14 15 16 17 18 19

ls和ls.str都支持通配符, 可以列出符合规则表达式的对象.

> ls(pattern= "a|b")
[1] "a" "b"
> ls.str(pattern= "a|b")
a :  int [1:10] 1 2 3 4 5 6 7 8 9 10
b :  int [1:10] 10 11 12 13 14 15 16 17 18 19

使用rm删除对象

> rm(a)
> a
Error: object 'a' not found

结合rm()和ls()可以删除所有对象

> rm(list=ls())

结合通配符, 可以删除符合通配符的对象.

rm(list=ls(pat="^m"))

接下来看看帮助相关的命令.

?cmd
help(cmd)
help("cmd")

以上三种都可以.

但是help("cmd")更通用, 例如要查询某些特殊符号的帮助, 例如乘法符号, 必须使用help("*"), 其他两种都不行.

> ?*
Error: unexpected '*' in "?*"
> help(*)
Error: unexpected '*' in "help(*"
> help("*")
Arithmetic                package:base                 R Documentation

Arithmetic Operators

Description:

     These unary and binary operators perform arithmetic on numeric or
     complex vectors (or objects which can be coerced to them).

Usage:

     + x
     - x
     x + y
     x - y
     x * y
     x / y
     x ^ y
     x %% y
     x %/% y
................

默认情况下, help只查询载入当前内存环境的包的信息, 如果你要查的命令或函数不在内存中, 需要给help加参数.

try.all.package = TRUE

例如: 

> help("bs")
No documentation for ‘bs’ in specified packages and libraries:
you could try ‘??bs’
> help("bs", try.all.package=TRUE)
Help for topic ‘bs’ is not in any loaded package but can be found in
the following packages:

  Package               Library
  splines               /usr/lib64/R/library

然后, 指定包名就可以查看其帮助了.

> help("bs", package = "splines")
bs                   package:splines                   R Documentation

B-Spline Basis for Polynomial Splines

Description:

     Generate the B-spline basis matrix for a polynomial spline.

Usage:

     bs(x, df = NULL, knots = NULL, degree = 3, intercept = FALSE,
        Boundary.knots = range(x))
...........

如果要查找帮助内容中包含某字符的函数, 可以使用help.search, 这个命令同样只在当前内存环境中查找, 如果要在所有包中查找, 需要加rebuild=TRUE选项.

> help.search("tree", rebuild = TRUE)
Help files with alias or concept or title matching ‘tree’ using regular
expression matching:

cluster::pltree         Clustering Trees - Generic Function
cluster::pltree.twins   Clustering Tree of a Hierarchical Clustering
codetools::showTree     Print Lisp-Style Representation of R Expression
datasets::Loblolly      Growth of Loblolly pine trees
datasets::Orange        Growth of Orange Trees
datasets::treering      Yearly Treering Data, -6000-1979
datasets::trees         Girth, Height and Volume for Black Cherry Trees
grid::current.viewport
                        Get the Current Grid Viewport (Tree)
grid::grob              Create Grid Graphical Objects, aka "Grob"s
grid::grid.reorder      Reorder the children of a gTree
grid::viewport          Create a Grid Viewport
grid::pushViewport      Maintaining and Navigating the Grid Viewport
                        Tree
MASS::Sitka             Growth Curves for Sitka Spruce Trees in 1988
MASS::Sitka89           Growth Curves for Sitka Spruce Trees in 1989
nlme::Spruce            Growth of Spruce Trees
rpart::rpart            Recursive Partitioning and Regression Trees
rpart::rpart.object     Recursive Partitioning and Regression Trees
                        Object
rpart::snip.rpart       Snip Subtrees of an Rpart Object
stats::cutree           Cut a Tree into Groups of Data
stats::dendrogram       General Tree Structures
tcltk::TkWidgets        Tk widgets

Type '?PKG::FOO' to inspect entries 'PKG::FOO', or 'TYPE?PKG::FOO' for
entries like 'PKG::FOO-TYPE'.

或者你可以使用两个问号, 和help.search效果一样.

如??tree

使用函数apropos则能找出所有在名字中含有指定字符串的函数，但只会

在被载入内存中的包中进行搜索.

例如, 包含help字符串的函数 : 

> apropos("help")
[1] "help"         "help.request" "help.search"  "help.start"

另外还有一个小技巧 : 

在R中操作时, 使用TAB键可以补齐.

好了, 就写到这里, 要善于使用帮助.

[参考]

?

help

help.search

ls

ls.str

rm

apropos

TAB