计算时间戳正在进行的事件数

Question

我有一系列时间戳标记某些事件的开始和结束.

library(chron)
start <- structure(c(14246.3805439815, 14246.3902662037, 14246.3909606481, 
14246.3992939815, 14246.4013773148, 14246.4034606481, 14246.4062384259, 
14246.4069328704, 14246.4069328704, 14246.4097106481, 14246.4097106481, 
14246.4104050926, 14246.4117939815, 14246.4117939815, 14246.4117939815, 
14246.4145717593, 14246.4152546296, 14246.4152662037, 14246.4152662037, 
14246.4159606481), format = structure(c("m/d/y", "h:m:s"), .Names = c("dates", 
"times")), origin = structure(c(1, 1, 1970), .Names = c("month", 
"day", "year")), class = c("chron", "dates", "times"))

finish <- structure(c(14246.436099537, 14246.4666550926, 14246.4083217593, 
14246.4374884259, 14246.4847106481, 14246.4867939815, 14246.4305439815, 
14246.4659606481, 14246.4520717593, 14246.9097106481, 14246.4930439815, 
14246.4763773148, 14246.4326273148, 14246.4291550926, 14246.4187384259, 
14246.9145717593, 14246.4395601852, 14246.4395717593, 14246.4395717593, 
14246.4367939815), format = structure(c("m/d/y", "h:m:s"), .Names = c("dates", 
"times")), origin = structure(c(1, 1, 1970), .Names = c("month", 
"day", "year")), class = c("chron", "dates", "times"))

events <- data.frame(start, finish)
head(event, 5)

                start              finish
1 (01/02/09 09:07:59) (01/02/09 10:27:59)
2 (01/02/09 09:21:59) (01/02/09 11:11:59)
3 (01/02/09 09:22:59) (01/02/09 09:47:59)
4 (01/02/09 09:34:59) (01/02/09 10:29:59)
5 (01/02/09 09:37:59) (01/02/09 11:37:59)

我现在想要计算在特定时间戳上正在进行的事件数量.

intervals <- structure(c(14246.3958333333, 14246.40625, 14246.4166666667, 
14246.4270833333, 14246.4375), format = structure(c("m/d/y", 
"h:m:s"), .Names = c("dates", "times")), origin = structure(c(1, 
1, 1970), .Names = c("month", "day", "year")), class = c("chron", 
"dates", "times"))

intervals

[1] (01/02/09 09:30:00) (01/02/09 09:45:00) (01/02/09 10:00:00) (01/02/09 10:15:00) (01/02/09 10:30:00)

所以我想要的输出如下:

            intervals count
1 (01/01/09 09:30:00)     3
2 (01/01/09 09:45:00)     7
3 (01/01/09 10:00:00)    19
4 (01/01/09 10:15:00)    18
5 (01/01/09 10:30:00)    12

虽然以编程方式解决问题是微不足道的,但我希望以210,000个间隔和超过120万个事件完成此任务.我目前的方法是利用data.table包和&操作员来检查间隔是否在每个事件的开始和结束时间之间.

library(data.table)
events <- data.table(events)
data.frame(intervals, count = sapply(1:5, function(i) sum(events[, start <= intervals[i] & intervals[i] <= finish])))

但考虑到我的数据大小,这种方法需要很长时间才能运行.关于在R中实现这一目标的更好替代方案的建议吗

干杯.

Answer 1

也许使用dim()代替sum()和ldply()代替sapply()可能会更快？

b<-function(i,df){ data.frame(i, count=dim(df[with(df, start<i & finish> i),])[1])};
ldply(intervals, b, events);

         i count
1 14246.40     3
2 14246.41     7
3 14246.42    19
4 14246.43    18
5 14246.44    12

我不熟悉 chron 库，所以我没有将其i作为时间戳显示出来。对不起。