如何使用dplyr和lubridate基于日期偏移从dfB提取数据填充dfA

• 第一步：加载所需工具包

library(dplyr)
library(lubridate)

• 第二步：统一两个数据框的日期格式，原始日期为「日/月/年」结构，使用lubridate的dmy()函数解析为标准日期类型

# 处理dfA的日期列
dfA <- dfA %>%
  mutate(Date = dmy(Date))

# 处理dfB的日期列
dfB <- dfB %>%
  mutate(Date = dmy(Date))

• 第三步：按偏移天数匹配dfB的字段，填充到dfA中
  通过多次左连接实现，每次连接对应一个偏移天数，匹配后重命名字段即可，以下为dplyr 1.1.0及以上版本的写法：

dfA_final <- dfA %>%
  # 匹配偏移1天的Event、Time（日期减1天）
  left_join(dfB %>% select(Date, Event, Time), by = join_by((Date - days(1)) == Date)) %>%
  rename(Event1 = Event, Time1 = Time) %>%
  # 匹配偏移2天的Event、Time（日期减2天）
  left_join(dfB %>% select(Date, Event, Time), by = join_by((Date - days(2)) == Date)) %>%
  rename(Event2 = Event, Time2 = Time) %>%
  # 匹配偏移3天的Event、Time（日期减3天）
  left_join(dfB %>% select(Date, Event, Time), by = join_by((Date - days(3)) == Date)) %>%
  rename(Event3 = Event, Time3 = Time)

如果使用低于1.1.0版本的dplyr，不支持join_by语法，可以用如下兼容写法：

dfA_final <- dfA %>%
  # 先生成临时偏移日期列
  mutate(date_offset1 = Date - days(1),
         date_offset2 = Date - days(2),
         date_offset3 = Date - days(3)) %>%
  # 逐列匹配
  left_join(dfB %>% select(Date, Event, Time) %>% rename(date_offset1 = Date, Event1 = Event, Time1 = Time), by = "date_offset1") %>%
  left_join(dfB %>% select(Date, Event, Time) %>% rename(date_offset2 = Date, Event2 = Event, Time2 = Time), by = "date_offset2") %>%
  left_join(dfB %>% select(Date, Event, Time) %>% rename(date_offset3 = Date, Event3 = Event, Time3 = Time), by = "date_offset3") %>%
  # 删除临时偏移列
  select(-starts_with("date_offset"))

注意：如果某一天的偏移日期在dfB中没有对应记录，对应字段会自动填充为NA，符合常规数据匹配逻辑。

内容的提问来源于stack exchange，提问作者RGR_288