script.R

toDateTime <- function(strTime){
  strptime((strTime),format="%Y/%m/%d %H:%M")
}

> toDateTime("2012/08/12 00:00")

----
countRunning <- function(recordDateTime, startDateTime, endDateTime){
  # isRunning <- ifelse(startDateTime <= recordDateTime & recordDateTime < endDateTime, 1, 0)
  isRunning <- (startDateTime <= recordDateTime & recordDateTime < endDateTime) * 1
  sum(isRunning)
}

> countRunning(toDateTime("2012/08/12 00:00"), data$startDateTime, data$EndDateTime)

----
# change for roop
countRunningForDateTimes <- function(recordDateTimes, startDateTime, endDateTime) {
  vec <- NULL
  for (recordDateTime in recordDateTimes) {
    vec <- append(vec, countRunning(recordDateTime, startDateTime, endDateTime))
  }
  vec
}

> recordDateTimes <- seq(min(data$startDateTime), max(data$endDateTime) + 1 , by = "secs")
> runningNums <- countRunningForDateTimes(recordDateTimes, data$startDateTime, data$endDateTime)

----
POSIXlt.floor <- function(POSIXltDateTime, by = "day") {
  mon  <- -1
  day  <- -1
  hour <- -1
  min  <- -1
  sec  <- -1

  if(by == "min") {
    sec  <- 0
  } else if(by == "hour") {
    min  <- 0
    sec  <- 0
  } else if(by == "day") {
  	hour <- 0
    sec  <- 0
    min  <- 0
  } else if(by == "month") {
  	day  <- 1
  	hour <- 0
    sec  <- 0
    min  <- 0
  } else if(by == "year") {
  	mon  <- 0
  	day  <- 1
  	hour <- 0
    sec  <- 0
    min  <- 0
  }

  if(mon  != -1) POSIXltDateTime$mon  <-  mon
  if(day  != -1) POSIXltDateTime$mday <-  day
  if(hour != -1) POSIXltDateTime$hour <-  hour
  if(min  != -1) POSIXltDateTime$min  <-  min
  if(sec  != -1) POSIXltDateTime$sec  <-  sec

  POSIXltDateTime
}

----
POSIXlt.ceiling <- function(POSIXltDateTime, by = "day") {
  dateTime <- POSIXlt.floor(POSIXltDateTime, by)

  if(by == "year" ) dateTime$year <-  dateTime$year + 1
  if(by == "month") dateTime$mon  <-  dateTime$mon  + 1
  if(by == "day"  ) dateTime$mday <-  dateTime$mday + 1
  if(by == "hour" ) dateTime$hour <-  dateTime$hour + 1
  if(by == "min"  ) dateTime$min  <-  dateTime$min  + 1
  if(by == "sec"  ) dateTime$sec  <-  dateTime$sec  + 1

  as.POSIXlt(as.POSIXct(dateTime))
}