#矩阵
?matrix
m<-matrix(1:6,nrow = 2,ncol=3,dimnames = list(c('r1','r2'),c('c1','c2','c3')))
m#默认按列排列
m<-matrix(1:6,nrow = 2,ncol=3,byrow = T,dimnames = list(c('r1','r2'),c('c1','c2','c3')))m
class(m)
m[1,1]  
m[1,]# 相当于 m[c(T,F),]
m[,1]
m['r1',]m[1,] <- c(100,99,98)
m
m[1,] <- 100
mt(m)#数组 维度可以大于2
?array
array(1:10)
array(1:10,dim = c(2,5))
array(1:12,c(2,3,2))dim1<-c('A1','A2')
dim2<-c('B1','B2','B3')
dim3<-c('C1','C2')
arr3<-array(1:12,c(2,3,2),dimnames = list(dim1,dim2,dim3))
arr3[,,'C1']
arr3[,,1]
arr3[,,c(T,F)]#数据框
data.frame()
student<-data.frame(ID=c(1001,1002,1003),NAME=c('lili','bob','sam'),GENDER=c('F','M','M'))
student
student<-data.frame(ID=c(1001,1002,1003),NAME=c('lili','bob','sam'),GENDER=c('F','M','M'),stringsAsFactors = F)
studentstudent[1,1]<-1009
student[1,]
student[,1]
student[,'ID'] #向量
student['ID'] #数据框
student$ID
student[c('ID','NAME')]
student#列表
list()
list1<-list(a=1,b='char',c=m,d=student)
list1
list1[[1]]
list1[['a']]
list1[[4]]
list1[['d']]
list1[4]
class(list1[4])#homework Q1
A<-matrix(1:12,nrow=3)
A
B<-matrix(1:12,ncol=4,byrow = T)
B#homework Q2
B[,1]<-100
B#homework Q3
wtdata<-data.frame(ID=c(1,2,3),name=c('张三','李四','王五'),stringsAsFactors = F,weight=c(60,70,80))
wtdata
str(wtdata)#homework   Q4
wtdata[c(1,3),]#homework Q5
wtlist<-list(a='A',b='B',c=wtdata)
wtlist#homework Q6
wtlist[[1]]