R 查找日期间隔包含准时日期的值

我有一个理论值的数据表，给出了一个区间：

firstDate   lastDate    theoric
2017-01-01  2017-01-03  10
2017-01-05  2017-01-25  20
2017-02-01  2017-08-31  30

另一方面，我有精确的测量值：

datetime      measured
2017-01-02       11
2017-01-08       22
2017-01-09       19
2017-01-26       25
2017-03-02       32

对于每个测量值，我想得到相应的理论值（其间隔包括测量日期）

注：1。理论区间不能重叠。2.如果测量值不在任何理论间隔内，则返回NA

预期产出：

datetime    measured  theoric
2017-01-02  11        10
2017-01-08  22        20
2017-01-09  19        20
2017-01-26  25        NA
2017-03-02  32        30

可复制数据集：

theoricDt <- structure(list(firstDate = structure(c(1483228800, 1483574400, 1485907200), class = c("POSIXct", "POSIXt"), tzone = "GMT"),     lastDate = structure(c(1483401600, 1485302400, 1504137600 ), class = c("POSIXct", "POSIXt"), tzone = "GMT"), theoric = c(10, 20, 30)), .Names = c("firstDate", "lastDate", "theoric"), row.names = c(NA, -3L), class = c("data.table", "data.frame"))
measureDt <- structure(list(datetime = structure(c(1483315200, 1483833600, 1483920000, 1485388800, 1488412800), class = c("POSIXct", "POSIXt"), tzone = "GMT"), measured = c(11, 22, 19, 25, 32)), .Names = c("datetime", "measured"), row.names = c(NA, -5L), class = c("data.table","data.frame"))

---

theoricDt您可以使用非等联接：

measureDt[theoricDt, on = .(datetime >= firstDate, datetime <= lastDate),
          theoric := i.theoric]

measureDt
#     datetime measured theoric
#1: 2017-01-02       11      10
#2: 2017-01-08       22      20
#3: 2017-01-09       19      20
#4: 2017-01-26       25      NA
#5: 2017-03-02       32      30

measureDt[Theoriicdt，on=（datetime>=firstDate，datetime