R

R 语言语法

1. 查看当前目录 getwd()
2. 切换指定目录 setwd()

1. Subsetting data选取数据

student[student$gender=='Female']

attach(student)
grade[Chinese>80,]
grade[Chinese>80 & Math>80,]
grade[Chinese>80 | Math>80,]
detach]

2. Sorting data

# sort by Chinese asc
order(grade$Chinese) # 排出升序的行号
oder(-grade$Chinese) # 进行降序的行号
grade[order(grade$Chinese),] #升序排序的dataFrame

# or use attach
attach(grade)

# sort by Chinese asc
grade[order(Chinese),]
# sort by Chinese asc, English des
grade[order(Chinese,-English),]
detach(grade)]

3. Merging data

# merging data by giving column names
total <- merge(student,grade,by="name")
head(total)

4. Aggregating Data

• aggregate(formula,data,FUN)

# compute the average Math grade by class
aggregate(Math~class, data=total,FUN=mean)

# compute the average grade by class and gender
aggregate(cbind(Chinese,Math,English,Science)~class+gender,data=total,FUN=mean)

Tips

paste(a,b,c) # 将所有内容组合出来，以sep=“ ”为分割

5. 自定义函数

Define a function:

function_name <- function (){
    ## Do something interesting 
    return(result)
}