R中的同时呼叫计数

Question

我想在电话系统上随时测量同时呼叫的数量。与SQL example相同，但使用R和CSV文件。

对于具有Id（数字），TimeOfCall（POSIXct），TimeOfClose（POSIXct）作为3列类型的CSV文件，我会执行以下操作，但我想知道是否有更高效的方式在R在Windows机器上）？

#Small dataset example. Much larger in reality 
id <- c(1,2,3,4) 

TimeOfStart <- c(as.POSIXct("2013-01-01 10:10:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-01-01 10:14:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-03-01 10:10:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-03-01 10:20:00", format="%Y-%d-%m %H:%M:%S")) 

TimeOfEnd <- c(as.POSIXct("2013-01-01 10:20:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-01-01 10:44:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-03-01 10:21:00", format="%Y-%d-%m %H:%M:%S"), as.POSIXct("2013-03-01 10:25:00", format="%Y-%d-%m %H:%M:%S")) 

call_data <- data.frame(id, TimeOfStart, TimeOfEnd) 

#holder for all POSIX converted to numeric entries 
stringoftimes <- '0' 

# loop through all rows and then concatenate all entries between start and end time after converting POSIX to numberics. 
for (i in 1:nrow(call_data)) 
{ 
    stringoftimes <- c(stringoftimes,c(as.numeric(call_data$TimeOfStart[i]):as.numeric(call_data$TimeOfStop[i]))) 

} 

#Convert to table so that count of entries takes place 
stringoftimes <- as.data.frame(table(stringoftimes)) 

#Sort table to see highest results first 
stringoftimes <- stringoftimes[order(stringoftimes$Freq, decreasing=TRUE),] 

Answer 1

Howsabout此则：

在时间点该序列的呼叫的计算数目，由分：

> t = seq(min(call_data$TimeOfStart),max(call_data$TimeOfEnd),by=60) 

功能是这样的：

> ncalls = Vectorize(function(t){sum(t>=call_data$TimeOfStart & t<=call_data$TimeOfEnd)}) 

剧情作为step功能：

> plot(t,ncalls(t),type="s")