r - 如何在 R 中查找值

Question

谁能帮忙，我有一个数据框( set_rise )，每一行包含当天的日落时间和第二天的日出时间。我有第二个数据框( data )，其中有一列日期/时间。我想在 data 中创建第二列通过获取 data 中的日期/时间，使用对应于白天或夜晚的字母并检查它是否在 set_rise 中的任何时间之间.

#df1- sunset, sunrise times
set_rise
                  set                rise 
1 2013-03-01 18:28:00 2013-03-02 08:27:00   
2 2013-03-02 18:31:00 2013-03-03 08:23:00    
3 2013-03-03 18:35:00 2013-03-04 08:19:00  
4 2013-03-04 18:38:00 2013-03-05 08:15:00   
5 2013-03-05 18:42:00 2013-03-06 08:12:00  
6 2013-03-06 18:45:00 2013-03-07 08:08:00   

#df2 my data    
  timedate
1 2013-03-01 19:00:00
2 2013-03-03 10:00:00
3 2013-03-06 00:01:00

我想要这样的输出

data
timedate night_day
2013-03-01 19:00:00  N
2013-03-03 10:00:00  D
2013-03-06 00:01:00  N

输出输入(set_rise)

dput(set_rise)
structure(list(set = structure(list(sec = 0, min = 28L, hour = 18L, 
mday = 1L, mon = 2L, year = 113L, wday = 5L, yday = 59L, 
isdst = 0L, zone = "WET", gmtoff = NA_integer_), .Names = c("sec", 
"min", "hour", "mday", "mon", "year", "wday", "yday", "isdst", 
 "zone", "gmtoff"), class = c("POSIXlt", "POSIXt")), rise = structure(list(
sec = 0, min = 27L, hour = 8L, mday = 2L, mon = 2L, year = 113L, 
wday = 6L, yday = 60L, isdst = 0L, zone = "WET", gmtoff = NA_integer_), .Names = c("sec", 
"min", "hour", "mday", "mon", "year", "wday", "yday", "isdst", 
"zone", "gmtoff"), class = c("POSIXlt", "POSIXt")), night = "N"), .Names = c("set", 
"rise", "night"), row.names = 1L, class = "data.frame")

来自 dput(data) 的输出

dput(data)
structure(list(timedate = structure(c(1362873600, 1362960000, 
1364342400), class = c("POSIXct", "POSIXt"))), .Names = "timedate",     row.names = c(NA, 
-3L), class = "data.frame")

Answer 1

这需要一些准备，但速度非常快。首先，您转换您的 set_rise至POSIXct (而不是 POSIXlt )。接下来，将日期转换为 numeric并结合所有的值，使它们形成白天和黑夜的交替值。然后，您调用findInterval告诉你 data 的每个日期的间隔落入:如果间隔是奇数，则为夜晚，否则为白天。所以:

#convert to POSIXct
set_rise[]<-lapply(set_rise,as.POSIXct)
#combine all the numeric values together
intervals<-c(t(matrix(c(as.numeric(set_rise$set),as.numeric(set_rise$rise)),ncol=2)))
#call findInterval and set the values, checking the parity
c("D","N")[1+(findInterval(as.numeric(data$timedate),intervals) %% 2)]
#[1] "N" "D" "N"