[R] longitudinal study

[bibek sharma]

Hello R user,
I have a data set from a longitudinal study ( sample below) where
subjects are followed over time. Second column (status) contains info
about if subject is dead or still in the  study and third column is
time measured in the week. Here is what I need: if status is not dead
or unknown take the last week, if status is dead or unknown I need to
have corresponding week.

Desired resulst:

1	no	7
2	yes	5
3	Unknown	4

Sample data
id	status	week
1	no	1
1	no	2
1	no	3
1	no	4
1	no	5
1	no	6
1	no	7
2	no	1
2	no	2
2	no 	3
2	no	4
2	yes	5
2	yes	6
2	na	7
2	na	8
2	na	9
3	no	1
3	no	2
3	no	3
3	Unknown	4
3	unknown	5
3	na	6
3	na	7
3	na	8

Any suggestion is much appreciated!
Thank you.
Bibek