Copyright © 2017 Xiaowan Liu

`In order to get R'resources more conveniently, I summary some useful commands in this article which is benefical to my R language's studying and is facilitate search for everyone surffing the net`

## Common-Commands

help.start()

`Starting browser， provide help with the format of HTML`

help.search()

`Allowing you to search something using any method which you want to employ`

example(topic)

`To see the demo of a topic`

source(“filename.R”)

`processing batch`

objects()

`Showing all of the names of Objects in the current environment`

`assign("var",c(3))`

and`var<-c(3)`

`Be equal to each other`

## Basic-Math-Commands

*log,exp,sin,cos,tan,sqrt,max,min,length,range,prod,var,sum,sort,order*

rep(x,times=5) & rep(x,each=5)

logical vector

value could equal

`TURE`

,`FALSE`

,`NA`

is.na(x)

judging whether x has NA element

is.nan(x)

judging whether x has NAN element

print(x,quote=F),parameter

`quote`

logical, indicating whether or not strings should be printed with surrounding quotes.

paste(x,y,sep=””)

paste vector x and y together use

`seq`

to separate`y <-x[-(1:5)]`

: exclude x[1:5]`mode`

and`length`

attributes(object)

access an object’s attributes.

as.character(x) & as.integer(digits)

class

numeric,logical,character,list,matrix,array,factor,data,frame

unclass

returns (a copy of) its argument with its class attribute removed.

factor(x)

encode a vector as a factor.

levels(factorname)

provides access to the levels attribute of a variable.

tapply(X, INDEX, FUN = NULL, …, default = NA, simplify = TRUE)

Apply a function to each cell of a ragged array, that is to each (non-empty) group of values given by a unique combination of the levels of certain factors.

dim(x) <-c(2,3,4)

abtain array x which is 2*3*4

array(x) & matrix(x)

`ab <- a`

%o% b or ` ab <- outer(a,b,”*”)