R刪除行的條目不是日期

Question

我有一個數據框，其中一列是（意味着）在00:00:00.0 yyyy-mm-dd形式的日期。大部分條目都是，但有些則不是。有沒有辦法刪除包含非日期的行？類似於（如果列是「日期」）

data <- data[is.Date(DATE)==TRUE,] 

例如，

Fruit Date 
apple 00:00:00.0 2005-02-01 
pear 00:00:00.0 2006-02-01 
orange 00:00:00.0 -8-2-402145 
rhino 00:00:00.0 2003-04-21 

我想

Fruit Date 
apple 00:00:00.0 2005-02-01 
pear 00:00:00.0 2006-02-01 
rhino 00:00:00.0 2003-04-21 

Answer 1

繼joran的推理：

# get the test data 
test <- data.frame(
    Fruit=c("apple","pear","orange","rhino"), 
    Date=c("00:00:00.0 2005-02-01", 
      "00:00:00.0 2006-02-01", 
      "00:00:00.0 -8-2-402145", 
      "00:00:00.0 2003-04-21") 
) 

# remove the rows by checking if not (!) an NA due to not meeting the date format 
test[!is.na(strptime(test$Date,format="00:00:00.0 %Y-%m-%d")),] 

結果：

Fruit     Date 
1 apple 00:00:00.0 2005-02-01 
2 pear 00:00:00.0 2006-02-01 
4 rhino 00:00:00.0 2003-04-21