问在R中保持一段时间的排名

EN

# create random data
plantId <- sample(1:50,1000,replace=TRUE)
rank    <- sample(1:5,1000,replace=TRUE)
time    <- as.POSIXct(sample(1000000:10000000,1000,replace=FALSE)+10000000*rank,origin="1970-01-01")
myData <- data.frame(plantId , rank, time )

# function to calculate the time a plant has a given rank
getRankTime <- function(id,testRank,data=myData){
  plantData <- myData[myData$plantId==id,];
  if(nrow(plantData) < 2){ # only one observed value of this plant
    return(NA)
  }else if(all(plantData$rank != testRank)){ # plant was never of the rank under consideration
    return(NA)   
  }else{ # calculate the (censered) time the plant stay(ed) in rank 'testRank'
    startObsTimeInRank <- min(plantData$time[plantData$rank == testRank])
    if(any(plantData$rank > testRank)){
      endObsTimeInRank <- min(plantData$time[plantData$rank > testRank])
    }else{
      #eighter take the last time
      endObsTimeInRank <- max(plantData$time[plantData$rank == testRank])  
      # alternatively use the current time
      # endObsTimeInRank <- Sys.time()
    }
    return(as.numeric(endObsTimeInRank - startObsTimeInRank))
  }
}

# calculate the average time plants stay in a rank
allPlantIds <- unique(myData$plantId)
stayInRankTime <- list()
for(runRank in 1:5){
  stayInRankTime[[runRank]] <- sapply(allPlantIds, function(runPlatId) getRankTime(runPlatId,runRank) )
}
# average time plants stay in acertain rank'
avgRankTime <- lapply(stayInRankTime,function(x)mean(x, na.rm =TRUE))
avgRankTime