我想找出最近一次策略重组的日期，在记录日期之前。在“reconType”不是NA的日期重构策略。抱歉，如果这个问题已经得到了回答，我一直在寻找了几天，但还没有能够找到任何东西。
下面是一个可重复的示例：

strategy <- rep(c('a', 'b', 'c'), each = 3)
date <- rep(c(as.Date("2023-01-02"), as.Date("2023-01-03"), as.Date("2023-01-04")), times = 3)
reconType <- c('Annual','NA','NA','Annual','Annual','NA','NA','Annual','NA')

df1 <- data.frame(strategy, date, reconType)

df1$lastDate <- max(df1$date[!is.na(df1$Recon.Type) &  df1$date < df1$date & df1$strategy == df1$strategy])
print(df1)

  strategy       date reconType lastDate
1        a 2023-01-02    Annual     <NA>
2        a 2023-01-03        NA     <NA>
3        a 2023-01-04        NA     <NA>
4        b 2023-01-02    Annual     <NA>
5        b 2023-01-03    Annual     <NA>
6        b 2023-01-04        NA     <NA>
7        c 2023-01-02        NA     <NA>
8        c 2023-01-03    Annual     <NA>
9        c 2023-01-04        NA     <NA>

但我想要的是：

strategy       date reconType lastDate
1        a 2023-01-02    Annual     <NA>
2        a 2023-01-03        NA     2023-01-02
3        a 2023-01-04        NA     2023-01-02
4        b 2023-01-02    Annual     <NA>
5        b 2023-01-03    Annual     2023-01-02
6        b 2023-01-04        NA     2023-01-03
7        c 2023-01-02        NA     <NA>
8        c 2023-01-03    Annual     <NA>
9        c 2023-01-04        NA     2023-01-03