假设我有一个数据框“数据”,其中包含测量变量 x 的时间序列数据:
date x
2009/10/01 00:00 10
2009/10/01 01:00 11
2009/10/01 02:00 12
2009/10/01 03:00 13
2009/10/01 04:00 14
2009/10/01 05:00 15
2009/10/01 06:00 16
2009/10/01 07:00 17
2009/10/01 08:00 18
2009/10/01 09:00 19
2009/10/01 10:00 20
2009/10/01 11:00 21
2009/10/01 12:00 22
2009/10/01 13:00 23
2009/10/01 14:00 24
2009/10/01 15:00 25
2009/10/01 16:00 26
2009/10/01 17:00 27
2009/10/01 18:00 28
2009/10/01 19:00 29
2009/10/01 20:00 30
2009/10/01 21:00 31
2009/10/01 22:00 32
2009/10/01 23:00 33
2009/10/02 00:00 34
...
另一个数据框“事件”具有由开始和停止日期定义的不同时间段:
id start stop
1 2009/10/01 02:00 2009/10/01 04:00
2 2009/10/01 07:00 2009/10/01 10:00
3 2009/10/01 08:00 2009/10/01 20:00
...
现在我想得到一个 x 在不同事件中的平均值表,如下所示:
id mean.x
1 13
2 18.5
3 25.5
在数据库中,我执行如下简单的 SQL 语句:
SELECT a.id, avg(b.x)
FROM events as a, data as b
WHERE b.date between a.start and a.stop
GROUP BY a.id
我想知道我怎么能在 R 中做这样的平均?如果我在数据中有一个 id 列指示哪个数据点属于哪个事件,我可以使用“聚合”,但我找不到创建此列的方法......
任何建议将不胜感激。
辛
编辑:
输入(数据):
structure(list(date = structure(c(1254348000, 1254351600, 1254355200,
1254358800, 1254362400, 1254366000, 1254369600, 1254373200, 1254376800,
1254380400, 1254384000, 1254387600, 1254391200, 1254394800, 1254398400,
1254402000, 1254405600, 1254409200, 1254412800, 1254416400, 1254420000,
1254423600, 1254427200, 1254430800, 1254434400), class = c("POSIXct",
"POSIXt"), tzone = "Europe/Berlin"), x = 10:34), .Names = c("date",
"x"), row.names = c(NA, -25L), class = "data.frame")
输入(事件):
structure(list(id = 1:3, start = structure(c(1254355200, 1254373200,
1254387600), class = c("POSIXct", "POSIXt"), tzone = "Europe/Berlin"),
stop = structure(c(1254362400, 1254384000, 1254420000), class = c("POSIXct",
"POSIXt"), tzone = "Europe/Berlin")), .Names = c("id", "start",
"stop"), row.names = c(NA, -3L), class = "data.frame")
编辑2:
输入(事件2):
structure(list(id = structure(1:3, .Label = c("AGH", "TRG", "ZUH"
), class = "factor"), start = structure(c(1254355200, 1254358800,
1254358800), class = c("POSIXct", "POSIXt"), tzone = "Europe/Berlin"),
stop = structure(c(1254362400, 1254384000, 1254420000), class = c("POSIXct",
"POSIXt"), tzone = "Europe/Berlin")), .Names = c("id", "start",
"stop"), row.names = c(NA, -3L), class = "data.frame")