如何计算 data.table 中的访问次数

Question

我需要在 R Studio 的数据表中创建一个新列，按“访问次数”对我的数据进行分类。

这是一个示例数据表：

library(data.table)
reprex_1 = data.table(
  `Receiver Number`=c("Receiver A", "Receiver B", "Receiver B","Receiver B","Receiver B", "Receiver B", "Receiver B","Receiver C", "Receiver C", "Receiver C"),
  Transmitter = c("Tag 1", "Tag 2" , "Tag 3" , "Tag 3",  "Tag 3" , "Tag 3" , "Tag 3","Tag 4" ,"Tag 4",  "Tag 4"),
  `Station Name` = c("Station A","Station B","Station B","Station B","Station B", "Station B","Station B","Station C","Station C","Station C"),
  TimeDiff = c( NA,NA,NA,221536,1114, 425,10728,110131,61,43)
)
Receiver Number  Transmitter Station Name TimeDiff
Receiver A       Tag 1       Station A       NA
Receiver B       Tag 2       Station B       NA
Receiver B       Tag 3       Station B       NA
Receiver B       Tag 3       Station B   221536
Receiver B       Tag 3       Station B     1114
Receiver B       Tag 3       Station B      425
Receiver B       Tag 3       Station B    10728
Receiver C       Tag 4       Station C   110131
Receiver C       Tag 4       Station C       61
Receiver C       Tag 4       Station C       43

我需要创建一个新的访问列，其中每次访问按接收器编号、发射器、站名和 TimeDiff 1800 或 NA 也构成新访问。我想要这个连续编号（1,2,3...）

这是我想要的：

Receiver Number Transmitter Station Name TimeDiff Visit
Receiver A       Tag 1      Station A       NA     1
Receiver B       Tag 2      Station B       NA     2
Receiver B       Tag 3      Station B       NA     3
Receiver B       Tag 3      Station B   221536     4
Receiver B       Tag 3      Station B     1114     4
Receiver B       Tag 3      Station B      425     4
Receiver B       Tag 3      Station B    10728     5
Receiver C       Tag 4      Station C   110131     6
Receiver C       Tag 4      Station C       61     6
Receiver C       Tag 4      Station C       43     6

我查看了基于分组数据对行进行分类的其他示例，并且可以让 R 根据前三列（接收器编号、发射器和站点名称）的唯一组合创建访问，但我不能弄清楚如何包含 TimeDiff >1800 的条件以启用新访问。

这是我可以达到的，但不包括通过 TimedDiff >1800 创建新访问：

require(data.table)
setDT(reprex_1)[,AttemptVisit:=.GRP, by = c("Receiver Number","Station Name", "Transmitter")]

Receiver Number Transmitter Station Name TimeDiff AttemptVisit
Receiver A       Tag 1    Station A       NA            1
Receiver B       Tag 2    Station B       NA            2
Receiver B       Tag 3    Station B       NA            3
Receiver B       Tag 3    Station B   221536            3
Receiver B       Tag 3    Station B     1114            3
Receiver B       Tag 3    Station B      425            3
Receiver B       Tag 3    Station B    10728            3
Receiver C       Tag 4    Station C   110131            4
Receiver C       Tag 4    Station C       61            4
Receiver C       Tag 4    Station C       43            4 

如果您能提供任何帮助，我将不胜感激！

Answer 1

我认为这应该可行。我们使用cumsum 的NA 或>1800 值作为分组的一部分：

reprex_1[, visit := .GRP,
         by = .(`Receiver Number`, Transmitter, `Station Name`, cumsum(TimeDiff > 1800 | is.na(TimeDiff)))]
# reprex_1
#     Receiver Number Transmitter Station Name TimeDiff visit
#  1:      Receiver A       Tag 1    Station A       NA     1
#  2:      Receiver B       Tag 2    Station B       NA     2
#  3:      Receiver B       Tag 3    Station B       NA     3
#  4:      Receiver B       Tag 3    Station B   221536     4
#  5:      Receiver B       Tag 3    Station B     1114     4
#  6:      Receiver B       Tag 3    Station B      425     4
#  7:      Receiver B       Tag 3    Station B    10728     5
#  8:      Receiver C       Tag 4    Station C   110131     6
#  9:      Receiver C       Tag 4    Station C       61     6
# 10:      Receiver C       Tag 4    Station C       43     6