关于比较的R switch语句

Question

我正在尝试编写一个R脚本来根据范围内的值拟合来评估不同的表达式.我们的想法是,如果长度在一个范围内,它将以一种方式进行评估,如果它在更长的范围内,它将以不同的方式进行评估.

我可以使用if/else语句来完成这项工作,但它非常难看,而且我确信必须有更好的方法......这里的代码可行.

Length=8.2

if (Length<1) 
    mode="Walk"
else if (1<=Length & Length <5)
    mode="bike" 
else if (5<=Length & Length <10)
    mode="drive"
else if (Length>=10)
    mode="fly"

我一直试图用switch函数做一些工作,但它似乎只能用于文本或整数...有没有办法让switch语句在每种情况下进行评估,比如这个？

Length=3.5

switch(Length,
       (Length<1)  mode="Walk"
       (1<=Length & Length <5)  mode="bike"
       (5<=Length & Length <10)  mode="drive"
       (Length=>10)  mode="fly"
)

Answer 1

这是Josh的类似答案,但使用findInterval:

Length <- 0:11

cuts <- c(-Inf, 1, 5, 10, Inf)
labs <- c("Walk", "bike", "drive", "fly")

labs[findInterval(Length, cuts)]
# [1] "Walk"  "bike"  "bike"  "bike"  "bike"  "drive" "drive"
# [8] "drive" "drive" "drive" "fly"   "fly"

你也可以使用嵌套ifelse语句,这是一个品味问题:

ifelse(Length < 1,  "Walk",
ifelse(Length < 5,  "bike",
ifelse(Length < 10, "drive",
                    "fly")))
# [1] "Walk"  "bike"  "bike"  "bike"  "bike"  "drive" "drive"
# [8] "drive" "drive" "drive" "fly"   "fly"

Answer 2

使用dplyr的case_when声明:

> library(dplyr)
> Length=3.5
> mode <- case_when(
                (Length < 1) ~ "Walk",
                (1 <= Length & Length < 5) ~ "bike",
                (5 <= Length & Length < 10) ~ "drive",
                (Length >= 10) ~ "fly"
          )
> mode
[1] "bike"

Answer 3

会cut()做你需要的吗？

Length <- 0:11

cuts <- c(-Inf, 1, 5, 10, Inf)
labs <- c("Walk", "bike", "drive", "fly")

as.character(cut(Length, breaks = cuts, labels = labs, include.lowest=TRUE))
#  [1] "Walk"  "Walk"  "bike"  "bike"  "bike"  "bike"  "drive" "drive" "drive"
# [10] "drive" "drive" "fly"