r - 是否有 R 函数可以查找列表中元素的下一个位置

Question

我想创建一个返回第二天的函数

这是我得到的:

next_day <- function(day){
 + week = list('monday','tuesday','wednesday','thursday','friday','saturday','sunday')
 + pos <- index(day, week)
 + if(day=='sunday') return('monday')
 + if match(day,week) return week[pos+1]

Error: unexpected symbol in:
"   + if(day=='sunday') return('monday')
    + if match"

Answer 1

nextday <- function(day){
  week <- list('monday','tuesday','wednesday','thursday','friday','saturday','sunday')
  day <- stringr::str_to_lower(day)
  index <- match(day, week)
  if(index == 7){
    index = 0
  }
  week[[index+1]]
}

nextday("sunday")

输出:

[1] "monday"