ifelse()函数 Usage ifelse(test, yes, no)
Example | 例子> ??ifelse> x <- c(1:10)> # 单次判断函数> ifelse(x<5,'T','F') [1] "T" "T" "T" "T" "F" "F" "F" "F" "F" "F"> # 函数嵌套应用> ifelse(x<5,ifelse(x<3, 'A','B'), 'C') [1] "A" "A" "B" "B" "C" "C" "C" "C" "C" "C"先从整体判断x<5的真假: 1. 大于5的记作"C"; 2. 小于5的再做判断; 小于3的记作"A"; 大于3(且小于5)的记作"B" 两者区别> a <- 0 > b <- c(1, 2, 3) > ifelse(a==0, b, 0) #把判断正确的'b'返回到'a'中 [1] 1 > if(a==0){b}else{0} [1] 1 2 3 > d <- c(1, 2, 3)> e <- 0 > ifelse(d==c(1, 2, 3), 1, 0) [1] 1 1 1 > if(d==c(1, 2, 3)){1}else{0} [1] 1 Warning message: In if (d == c(1, 2, 3)) { : 条件的长度大于一,因此只能用其第一元素 ifelse()与if(){}else(){}的区别:
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