Colleagues

After reading in some clinical data, I discovered that the subject ID  
column contains entries only for the first record for each  
individual; subsequent rows are recorded as NA.  For example:
> 1
> NA
> NA
> NA
> NA
> 2
> NA
> NA
> NA
> NA
> 3
> NA
> NA
> ...

I can think of various approaches to replace the NA values with  
appropriate entries.  I could loop through each row - if the value is  
NA, I replace it with the entry from the row above.  Or, I could find  
the positions of the non-NA values with match, then replace groups of  
entries (e.g., positions 2-5) with appropriate entries, again with a  
loop.

But, I expect that R allows some more clever approach to the  
problem.  Any thoughts?

Dennis

Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-415-564-2220
www.PLessThan.com


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