R:如何根据时间和日期查找计数

Question

我想要实现的目标是计算给定的星期几和小时内发生的事件数量

示例数据:

Date            Time
2007-07-20   11:00:00
2007-01-05   06:15:00
2007-12-11   23:55:00
2007-12-11   23:55:00

到

输出:

 Day    Hour      Count
Friday  11:00 AM     1
Friday  6:00 AM      1 
Friday  11:00 PM     2

非常感谢任何帮助!

谢谢!

Answer 1

Base R 也能很好地应对这个问题:

aggregate(
  count ~ wkday + hour,
  data=transform(dat,
                 wkday=format(as.Date(Date), "%A"),
                 hour=format(as.POSIXct(Time,format="%H:%M:%S"), "%I %p"),
                 count=1),
  FUN=sum
)
#    wkday  hour count
#1  Friday 06 AM     1
#2  Friday 11 AM     1
#3 Tuesday 11 PM     2

dat 所在位置:

dat <- structure(list(Date = c("2007-07-20", "2007-01-05", "2007-12-11", 
"2007-12-11"), Time = c("11:00:00", "06:15:00", "23:55:00", "23:55:00"
)), .Names = c("Date", "Time"), row.names = c(NA, -4L), class = "data.frame")