药物切换模式

问：

我正在尝试从处方数据中研究药物转换模式，如表所示（dput的结果）：

    structure(list(ID = c("A2M8K", "A2M8K", "A2M8K", "A2M8K", "A2M8K", 
"D2N4", "D2N4", "D2N4", "D2N4", "D2N4", "D13L", "D13L", "D13L", 
"D13L", "D13L", "D13L", "D13L", "D13L", "D13L", "D13L"), Class = c("Biguanides ", 
"Sulfonylureas", "Sulfonylureas", "Biguanides ", "Sulfonylureas", 
"DPP ", "Sulfonylureas", "GLP ", "GLP ", "Sulfonylureas", "Biguanides ", 
"Sulfonylureas", "Biguanides ", "Sulfonylureas", "DPP ", "Insulins", 
"Biguanides ", "Sulfonylureas", "Insulins", "Biguanides "), start_date = c("7/1/2018", 
"7/1/2018", "10/3/2018", "8/27/2020", "8/27/2020", "7/31/2019", 
"7/31/2019", "3/1/2020", "6/15/2020", "6/15/2020", "2/15/2016", 
"2/15/2016", "2/20/2017", "2/20/2017", "1/21/2018", "7/26/2018", 
"5/15/2019", "5/15/2019", "7/24/2019", "1/30/2020"), end_date = c("6/22/2020", 
"8/30/2018", "6/22/2020", "10/26/2020", "10/26/2020", "10/29/2019", 
"3/28/2020", "3/31/2020", "10/8/2020", "10/13/2020", "11/9/2016", 
"11/9/2016", "10/24/2018", "10/24/2018", "4/21/2018", "10/29/2018", 
"10/22/2019", "10/22/2019", "10/22/2019", "11/25/2020")), row.names = c(NA, 
20L), class = "data.frame")

我在 R 中尝试了以下方法：

###DF sample:
med_changes <- data.frame(ID = character(),
                          Change.type = character(),
                          Med.change = character(),
                          stringsAsFactors = FALSE)
#arrange:
library(dplyr)
prescriptions <- prescriptions %>%
  group_by(ID) %>%
  mutate(prev_med = lag(Class),
         prev_date = lag(end_date)) %>%
  ungroup() %>%
  filter(!is.na(prev_med))
### Switch: 
med_changes <- prescriptions %>%
  filter(as.numeric(difftime(start_date, prev_date, units = "days")) > 60) %>%
   mutate(Change.type = "Switch",
       Med.change = paste(prev_med, "to", Class),
       Time.to.change = as.numeric(difftime(start_date, prev_date, units = "days"))) %>%
  select(ID, Change.type, Med.change, Time.to.change)

### Add-On:
add_on <- prescriptions %>%
  filter(as.numeric(difftime(start_date, prev_date, units = "days")) > -60 & as.numeric(difftime(start_date, prev_date, units = "days")) <= 60) %>%
  mutate(Change.type = "Add-on",
         Med.change = paste(prev_med, "added to", Class),
         Time.to.change = as.numeric(difftime(start_date, prev_date, units = "days"))) %>%
  select(ID, Change.type, Med.change, Time.to.change)

med_changes <- rbind(med_changes, add_on)

然而，这并没有考虑到起始治疗方案;如果两种药物具有相同的开始日期，则意味着患者开始接受多种方案治疗（多种药物），并且应检查所有先前方案类别中的下一行类别，以确定它是否被添加或切换或没有任何变化。

我正在寻找的结果类似于以下内容：

我有没有办法修改这个脚本来做到这一点，或者如果你能推荐一个包来做到这一点，我将不胜感激。