st: how to get the mean value for this panel data?

[Hey Sky <heyskywalker@yahoo.com>]

Dear Stataers

I have met a problem to calculate mean value in panel data. example data and 
detail of my question as follows. 


* example data
clear
input id jobid wage1 wage2 wage3 
1 1 1 2 .
1 2 . 3 .
2 1 1 . .
2 2 . 2 2
3 1 1 2 .
3 2 . 3 .
3 3 . . 4
4 1 2 4 6
5 1 2 3 .
6 1 2 . 4
end
 
 
the wage1~3 represents the wages in each wave if the person works. for example, 
the id=1 person works in 1st and 2nd wave but not 3rd. he switches job in 2nd 
wave thus he has two wage for jobid=1, his first job. surely for id=2 person, he 
has two jobs, switches job in 2nd wave and keeps it till 3rd wave. for id=4, he 
keeps his job for all 3 waves and id=5 lost his only job in 3rd wave. 


now, I need to get a mean wage for this 3 waves panel data. if they have not 
switched job, use this job's wage in each wave to calculate the mean wage; 
otherwise, use the new job wage in a new wave. 


for example,for people who did not switch job, such as id=4, the mean wage 
should equal to (2+4+6)/3, which egen x=rowmean(wage1 wage2 wage3) can do. but 
how about id=1? his mean wage should equal to (1+3)/2; or id=2, mean 
wage=(1+2+2)/3; and id=3, mean wage=(1+3+4)/3. how to have a code to deal with 
all these situations automatically? 


I have thousands obs in my real data. thus it is impossible to do it by hand. 
thanks  for any suggestions.



*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/