R学习 数据结构和简单处理

c(1,2,3,4)
c("1","2","3","4")
c(TRUE,FALSE)
c(1:4)

rep("x",times = 4)#重复
seq(from = 2,to = 16,by = 2)#参数名称可省，2到16间每2个数取一个
rnorm(n = 4)#随机取4个数
paste0(rep("x",times = 3),1:3)#两两组合，无间隔符
paste(rep("x",times = 3),1:3,sep=",")#两两组合，有间隔符，默认为空格

y<-matrix(1:20,nrow = 5,ncol = 4,byrow=T)

data() #列出已载入的包中的所有数据集
data(package =.packages(all.available = TRUE)) #列出已安装的包中的所有数据集

name<-c("A","B","C","D")
age<-rep(10,times=4)
grade<-c("good","poor","poor","good")
df<-data.frame(name,age,grade)
df

df[1]#第一列
df$age
df[,c("age","name")]#按列名取
df[c(1,4),1:3]#1、4行，1到3列

df[2,2] <- 11#改一个
df$grade<-c("good","good","good","good")#改一列
colnames(df)[2] <- "年龄"#改第二行行名，列名为rownames(df)

df$class <- c(2,2,3,4)#后接不存在的行名

test1 <- data.frame(name = c('jimmy','nicker','Damon','Sophie'), 
                    blood_type = c("A","B","O","AB"))
test1
test2 <- data.frame(name = c('Damon','jimmy','nicker','tony'),
                    group = c("group1","group1","group2","group2"),
                    vision = c(4.2,4.3,4.9,4.5))
test2

test3 <- data.frame(NAME = c('Damon','jimmy','nicker','tony'),
                    weight = c(140,145,110,138))
test3
merge(test1,test2,by="name")
merge(test1,test3,by.x = "name",by.y = "NAME")

df$class[df$class>2]