R-Language Review notes-record details

> With (mtcars,summary (mpg,disp))   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.    10.40   15.42   19.20   20.09   22.80   

Equivalent to attach and detach

> mydata=transform (mtcars,sumx=mpg+disp)

Add a new variable to the data frame same as Mydsta$sumx

> View (MyData)

A small box will pop up to view the data

> Within (leadership,{
+ Agecat=na
+ agecat[age>75]= ' Elder '
+ agecat[age<55]= ' young '})

The difference between with and within is that with no modification to the data frame, within can

#对变量的名称进行修改

1) >fix (data) #进行交互式修改

2) reshape package of rename rename (Data,c (oldname= ' newname ', oldname= ' newname '))

3) names (data) [i]= ' NewName '

#移除含有缺失值的观测

1) na.nmit (data)

#日期的输出格式

>format (x,format= '%d%m%y ')

#输出系统日期

>sys.date ()

#计算时间间隔

Difftime (today,anotherday,units= ' weeks ') #返回的为一种特定的类, convert it using as.numeric if needed

#数据排序

> Order (MTCARS$MPG) #返回的为mpg升序排列 (default, if you want to add a symbol before a variable in descending order, or set a parameter) index number

[1] 7, 6, 5, 1, 2, 4, 3, 9, +--ten

So to Mtcars[order (Mtcars$mpg),] only return data

#数据集的合并

>total=merge (dataframea,dataframeb,by= ' id ') is merged #数据依据 ' ID ', equivalent to inner join

The data set contains the judgment of using%in%, which returns a logical vector

#删除变量可以用c (-1) or Var1=null

#依据条件选取观测值

Newdata=subset (Leadership,age>=35,select=c (Q1,Q2))

The form of Newdata=subset (LEADERSHIP,AGE>=35,SELECT=GENDER:Q4) is applied only here to the selection of variables

> mtcars[1:10, ' mpg '] must be double-quoted

#随机抽样

>sample (x, size, replace = FALSE, prob = NULL)

> Sample (1:10,3)
[1] 5 7 3

The "Sqldf" package can be used to use SQL statements

R-Language Review notes-record details