st: Coding for multiple visits data

[Tasha Amin <tamin_wh@hotmail.com>]

My data has multiple visits and is coded in the following way, where a person appears as a case=1 from visit 1.....(see first set of code), even though ID 1 should be case=1 from visit 6, after 2 successive 0's in RNA, ie SHOULD look like second set of code. How do I get case to accurately change at the right visit? Thanks!
 
Looks like:
ID visit RNA case
1 1 1 1       
1 3 1 1        
1 5 0 1  
1 6 0 1            
1 7 0 1 
2 1 1 0
2 2 1 0
2 3 1 0 
2 4 1 0
 
Want it to look like:
ID visit RNA case
1 1 1 0       
1 3 1 0        
1 5 0 1  
1 6 0 1            
1 7 0 1 
2 1 1 0
2 2 1 0
2 3 1 0 
2 4 1 0  		 	   		  
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