R language learning basis (1)

Reference materials: a PPT (I do not know who) & "153 minutes to learn R"

• Auto-completion command:
  Tab key can automatically complete R command;
  using the Tab key twice to return all possible completions command list.
• Clear variables:
  using RM () function,
  clear the variable x, rm(x)
  clear all variables,
  RM (LS List = (All = TRUE))
• After changing the display decimal digits
  used Options (= digits)
  digits parameter can be from 1 to 22, the default is 7.
• Call system program
  used sysytem () function, or by shell.exec ()
  , such as:
  System ( "Notepad")
  shell.exec ( "C: / the WINDOWS / Clock")
• What CRAN that?
  Comprehensive R Archive Network, is to have the same information, including a collection of networks release version of R, package, documentation and source code.
• R upgrade, but do not want to reinstall Packages
  to copy the files in the old version remains the library directory to the new version of the library catalog, then update.packages ();
  or unload R, the R attached to the old catalog, and then update. packages ()
• Uninstall Packages already installed

remove.packages(c("pkg1","pkg2"),lib=file.path("path","to","library"))

• View R's working directory
  using the getwd()命令get working directory of R;
  use setwd()命令to set the working directory location;
  the working directory: working directory
• Save the
  use save.image()函数, Rdata saved to a file;
  use save (..., file =) R stored objects;
• R meaning the initial state of loading the package

packages	description
stats	Commonly used statistical functions
graphics	Basic drawing functions
grDevices	Base or grid graphics device
utils	R tool function
datasets	Basic data set
methods	R class defines methods and tools for programming objects and
base	Basis function

• View currently loaded packages
  use search()函数
.packages(all.available = TRUE)to get a list of locally installed packages
• Built using the R data sets
  data()函数can be loaded into memory;
• Data type
  R not a scalar, vector storage by various types of data.
  Wherein factorfactor, used for labeling the sample.

Not yet fathom ......

• dataframe
  Matrix data block, a data set loose, can consist of different types of columns (number, factors, characters and the like) composed (matrix-like).
• Function Code
  Enter function name carriage return;
  if it is a function of the class, consider using methods（类函数名）can see the list of functions, find a specific function, enter it, then Enter.
• View matrix before and after a few lines
  head()函数;tail()函数
• Meaning of formula symbols

Symbolic expression	effect	meaning
+ Or:	Variable connection	Interactions between variables
*	-	a*b=a+b+a:b
^	-	(a+b+c)^2=(a+b+c)*(a+b+c)
-	-	Removed, (a + b + c) ^ 2-a: b = a + b + c + b: c + a: c
.	-	Update () is the function already represented

• Reads the data portion
  using foreign包, read some statistical data software;
  read the data in Excel, the recommended method is: first Excel file saved as csv file (comma separated values), useread.csv()函数
• Call output
  capture.output()函数: the output of R into a character or a file.
• Read and write data directly from memory
  to use read.table("clipboard");write.table("clipboard")
• The factor into digital
  as.numeric(as.character(f))
as.numeric(levels(f))[as.integer(f)]
• Input data using a spreadsheet
  edit()函数andfix()函数