迄今为止的第一个转换是as.Date。对日期进行排序，然后使用sapply，定义next_meeting后使用difftime：

meetings <- as.Date(c("2023-06-21", "2023-05-03", "2023-03-22", "2023-02-01", "2022-12-07"))
dates <- as.Date(c("2023-08-01", "2023-04-01", "2023-03-01", "2023-02-01", "2023-01-01"))

meetings <- sort(meetings)

sapply(dates, function(date) {
  next_meeting <- meetings[which(meetings >= date)][1]
  if (is.na(next_meeting)) {
    return(NA)
  } else {
    return(as.integer(difftime(next_meeting, date, units = "days")))
  }
})

产出：

[1] NA 32 21  0 31

这也可以在dplyr 1.1.0+中使用join_by和closest来完成：

left_join(data.frame(dates = as.Date(dates)),
          data.frame(meetings = as.Date(meetings)),
          join_by(closest(dates <= meetings))) |>
  mutate(next_meeting = as.numeric(meetings - dates))


       dates   meetings next_meeting
1 2023-08-01       <NA>           NA
2 2023-04-01 2023-05-03           32
3 2023-03-01 2023-03-22           21
4 2023-02-01 2023-02-01            0
5 2023-01-01 2023-02-01           31