通过R中的特定列填写缺少值的缺失日期

I have the following table:

我有下表:

Name        Date       Quiz    Homework   
John      11-01-02      40        10
John      11-01-03      47        20
John      11-01-04      41        10
John      11-01-08      35        10
John      11-01-10      43        15
John      11-01-13      40        10
Adam      11-01-05      41        10
Adam      11-01-08      41        15
Adam      11-01-14      49        10
Adam      11-01-19      40        20
Adam      11-01-21      40        10
Name