R语言中ifelse、which、%in%的用法详解

ifelse(test,yes,no)

x = 5
ifelse(x,1,0)

which(test，arr.ind=FALSE)

which(LETTERS == "R")

element %in% list veator

1 %in% c(1:3)

if (7<10) {
  print("Seven is less than ten")
} else{
  print("seven is more than ten")
}

Titanic=read.csv("https://Goo.gl/4Gqsnz")  #从网络读取数据

#any代表只要有任一值符合，即为TRUE
if (any(titanicC$Age>70)) {                                              
  print("there are passengers older than 70")
} else{
  print("no one is older than 70")
}

#所有都满足才true
if (all(titanicC$Age>10)) {
  print("all passengers older than 10")
} else{
  print("there are passengers younger than 10")
}

#放的位置决定是删除单一变量缺失值，还是删除任何变量缺失值
if (any(na.omit(titanic$Age==100))) {
  print("there are passengers aged 100")
} else{
  print("there are no passengers aged 100")
}                                                                                 
#数据库中只要有missing的记录都删掉
if (any(titanic$Age==80, na.rm=TRUE)) {
  print("there are passengers aged 80")
} else{
  print("there are no passengers aged 80")
}       
#Age这个变量有missing的记录删掉，其他变量有missing可以保留

x=100
y=10
if(x<y){
  print("AA")
} else if(x==y){
  print(BB)
} else{
  print(CC)
}