dplyr 中的排名函数

Question

我有一个示例 df，如下所示:

d<-structure(list(ReviewType= c("Review","Review","Review","Correction","Correction","Review","Review","Review","Review","Review","Correction","Correction","Deficiency","Correction","Correction", 
                                "Deficiency", "Deficiency", "Deficiency", "Correction","Correction","Deficiency","Correction"),
                  Submissiondate= c("2020-08-29 04:32:00","2020-08-28 04:31:00","2020-08-26 04:31:00","2020-08-25 04:31:00","2020-08-24 04:31:00","2020-08-23 04:31:00","2020-08-22 04:31:00","2020-08-21 04:31:00","2020-08-20 04:31:00","2020-08-19 04:31:00",
                                    "2020-09-27 04:31:00","2020-09-27 03:52:59","2020-09-28 17:30:00","2020-09-29 14:01:00",
                                    "2020-09-05 03:00:00","2020-09-05 03:51:00", "2020-09-03 23:59:49",
                                    "2020-09-02 00:03:54","2020-09-01 00:04:48","2020-10-01 04:31:00","2020-10-11 04:31:00","2020-10-21 04:31:00"),
                  CaseNo= c("124","123","125","121","121","125","123","123","123","123","123","123","123","125","123","123","123","124","123","127","127","127")), class = "data.frame", row.names = c(NA, -22L))

我知道我可以使用排名函数来获取每种情况的最新详细信息，如下所示

d<-d %>% group_by(CaseNo) %>% arrange(desc(Submissiondate)) %>% dplyr::mutate(rank = row_number()) %>% arrange(`CaseNo`, rank)%>%filter(rank==1)

但是，是否可以使用此排名功能来获取特定日期的最新详细信息？例如，在我的 df 中，如果我想了解到 2020 年 8 月 29 日每个案例的最新评论类型是什么？我应该如何继续这样做？

Answer 1

您可能需要考虑使用与最大值的比较，导致更少的计算和更少的打字:

d %>% 
  group_by(CaseNo) %>%
  filter(Submissiondate==max(Submissiondate))

或者针对您的问题:

d %>% 
  filter(as.Date(Submissiondate)<"2020-08-30") %>%
  group_by(CaseNo) %>%
  filter(Submissiondate==max(Submissiondate))

如果您对短代码和速度感兴趣，这里还有一个 data.table 版本:

D <- data.table(d)

D[,.SD[Submissiondate==max(Submissiondate)], keyby=CaseNo]

D[Submissiondate<"2020-08-30", .SD[Submissiondate==max(Submissiondate)], keyby=CaseNo]