﻿ 什么是从数据帧中的带时间戳的行分区和聚合间隔的有效方法？ - 代码日志

#### 什么是从数据帧中的带时间戳的行分区和聚合间隔的有效方法？

>“2010-01-13 03:02:38 UTC”
>“2010-01-13 03:08:14 UTC”
>“2010-01-13 03:14:52 UTC”

>“2010-01-13 03:20:42 UTC”
>“2010-01-13 03:22:19 UTC”

cut使用喜欢如此：

``````interv <- function(x, start, period, num.intervals) {
return(cut(x, as.POSIXlt(start)+0:num.intervals*period))
}
``````

``````v <- as.POSIXct(c(
"2010-01-13 03:02:38 UTC",
"2010-01-13 03:08:14 UTC",
"2010-01-13 03:14:52 UTC",
"2010-01-13 03:20:42 UTC",
"2010-01-13 03:22:19 UTC"
))

interv(v, as.POSIXlt("2010-01-13 03:00:00 UTC"), 900)
# [[1]]
# [1] "2010-01-13 03:00:00"
# [[2]]
# [1] "2010-01-13 03:00:00"
# [[3]]
# [1] "2010-01-13 03:00:00"
# [[4]]
# [1] "2010-01-13 03:15:00 CET"
# [[5]]
# [1] "2010-01-13 03:15:00 CET"

# cut returns factor, you must provide proper breaks:
cut(v, as.POSIXlt("2010-01-13 03:00:00 UTC")+0:2*900)
# [1] 2010-01-13 03:00:00 2010-01-13 03:00:00 2010-01-13 03:00:00
# [4] 2010-01-13 03:15:00 2010-01-13 03:15:00
# Levels: 2010-01-13 03:00:00 2010-01-13 03:15:00

# findInterval returns vector of interval id (breaks like in cut)
findInterval(v, as.POSIXlt("2010-01-13 03:00:00 UTC")+0:2*900)
# [1] 1 1 1 2 2
``````

``````cut(v,"15 min")
# [1] 2010-01-13 03:02:00 2010-01-13 03:02:00 2010-01-13 03:02:00
# [4] 2010-01-13 03:17:00 2010-01-13 03:17:00
# Levels: 2010-01-13 03:02:00 2010-01-13 03:17:00
``````