在R中选择案例中的案例

Question

很抱歉，这似乎是一个愚蠢的问题，但我想问一问，在case中，switch case语句中的case是否必须始终是一个字符串？以下代码抛出错误：

day = 2
weekday <- switch(day,
                  1 = "Sunday",
                  2 = "Monday",
                  3 = "Tuesday",
                  4 = "Wednesday",
                  5 = "Thursday", 
                  6 = "Friday",
                  7 = "Saturday",
                  "Invalid Input!!")
print(weekday)

但是此代码非常有效：

day = 2
weekday <- switch(day,
                  '1' = "Sunday",
                  '2' = "Monday",
                  '3' = "Tuesday",
                  '4' = "Wednesday",
                  '5' = "Thursday", 
                  '6' = "Friday",
                  '7' = "Saturday",
                  "Invalid Input!!")
print(weekday)

哪一天是数字，在转换情况下与字符匹配？

Answer 1

如果在switch()中测试的表达式是数字，则大小写按位置匹配，因此可以省去参数名称并执行：

day = 2
weekday <- switch(day,
                  "Sunday",
                  "Monday",
                  "Tuesday",
                  "Wednesday",
                  "Thursday", 
                  "Friday",
                  "Saturday",
                  "Invalid Input!!")
print(weekday)
# Output:
# [1] "Monday"