st: A loop for S.D. or Mean in Panel Data set

[Asgar Khademvatani <akhademv@ucalgary.ca>]

Dear All friends,

Hope you are fine. I am using stata 8.2 platform in Windows. I have 
loaded a panel data set in a long-format  for 4 sectors each sketched 
from 1958 to2000. Thus, I have 172 observations for each variable. My 
target is calculating S.D or mean cross-4 sectors for each year and 
graph over time. For more clarity, for instance, I would like to 
calculate S.D. of 4-sectors for year 1958. In doing so, I need to have a 
loop to use observations numbers: 1, 45, 87, and 131 in calculation of 
S.D for year 1958, and this continues for calculation of S.D 
cross-sectors for other years, and so on and so forth. I understand I 
must write a "for values loop"  for performing such calculations of S.D 
or mean for each year cross-sectors.  I am not sure how to initiate such 
for values loop or another solution in Stata. May somebody help me out 
on this matter?

Your help is much appreciated  in advance.

Thanks
Asgar Kh.
University of Calgary-Canada
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