R-notes-introductory

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,”*”)