Question

假设我们创建了一个像这样的data.frame：

> hugs_per_day <- rnorm(10)
> hugs_per_day <- as.data.frame(hugs_per_day)
> hugs_per_day
   hugs_per_day
1  -2.500457495
2  -0.204545274
3  -0.955424927
4   0.320184701
5   1.822908001
6  -0.058679520
7  -0.276004919
8   0.175341993
9  -0.137404974
10  0.005096691

我们希望每天运行一个函数来根据结果返回一个值，如下所示：

nested_ifelse <- function(x){

ifelse (x > 1,     mood <- "happy",
    ifelse(x < 0,  mood <- "sad", 
                   mood <- "same as yesterday" ))

   return(mood)
}

nested_ifelse（）示例执行我想要的操作，我确信sapply（）是正确的R函数，用函数的结果填充新列，但我不能把它们放在一起。

Answer 1

您没有使用set.seed，因此该示例不可重现，但这应该为您提供所请求的向量：

    hugs_per_day$mood <- c("sad","same as yesterday","happy" )[
              findInterval(  hugs_per_day$hugs_per_day, c(-Inf, 0, 1) ) ]
    hugs_per_day
       hugs_per_day              mood
    1     0.5747557 same as yesterday
    2    -1.0236557               sad
    3    -0.0151383               sad
    4    -0.9359486               sad
    5     1.1022975             happy
    6    -0.4755931               sad
    7    -0.7094400               sad
    8    -0.5012581               sad
    9    -1.6290935               sad
    10   -1.1676193               sad

Answer 2

nested_ifelse应该是这样的：

nested_ifelse <- function(x){
  mood <- ifelse (x > 1,   "happy",
    ifelse(x < 0, "sad", 
    "same as yesterday" ))
  return(mood)
}

或更简单地说，

nested_ifelse <- function(x)
  ifelse (x > 1,   "happy",
  ifelse(x < 0, "sad", 
  "same as yesterday" ))

你可以像这样使用：

d$mood2 <- sapply(d$v, nested_ifelse)

但实际上你不需要在这里打电话：

d$mood <- nested_ifelse(d$v)

就够了。

数据d应该是这样的......

d <- data.frame(v=rnorm(10))

Answer 3

我不确定这是否适用于您的实际问题，但我想我会指出您并不总是需要嵌套ifelse函数。有时您可以按顺序使用它们，只需确保顺序正确，这样就不会覆盖以前的值。

set.seed(229)
hugs_per_day <- data.frame(hugs=rnorm(10))

hugs_per_day$mood <- "same as yesterday"
hugs_per_day$mood <- with(hugs_per_day, ifelse(hugs > 1, "happy", mood))
hugs_per_day$mood <- with(hugs_per_day, ifelse(hugs < 0, "sad", mood))

嵌套的ifelse R函数传递给sapply（）以创建新的data.frame

3 个答案: