st: Increase observations by group and then calculate percentages

[Catherine Tisch <catherine.tisch@canterbury.ac.nz>]

Hi all

I'm hoping someone can help me with my problem - I'd like to insert an
observation after every group and then create percentages by group in my
panel dataset.

My dataset looks something like this:

AreaID	Ethnicity	Sex1Age1	Sex2Age1	Sex1Age2
Sex2Age2	and so on....	 
1	GroupX	18		16
1	Total		57		21
2	GroupX	33		81
2	Total		528		147
and so on....

Ethnicity is stored as a string, all other variables are stored as
float.  I have approximately 2000 AreaIDs and 16 Sex/Age groups.  I am
using Stata 11.1.

I'm hoping my final dataset might look something like this:

AreaID	Ethnicity	Sex1Age1	Sex2Age1	Sex1Age2
Sex2Age2	and so on....	 
1	GroupX	18		16
1	Total		57		21
1	PercentX	31.6		76.2
2	GroupX	33		81
2	Total		528		147
2	PercentX	6.3		55.1
and so on.....

Where PercentX is GroupX/Total for each AreaID by the Sex/Age variables.

I think the first stage I need to do is increase the number of
observations in my dataset by using -set obs-.  I tried

set obs `=_N+1', by AreaID

but got the error message 'options not allowed'.  How can I get around
this?  

Once I get that sorted, the second stage is calculating percentages and
I think I need to use -by- function and any suggestions would be most
welcome.  


Cheers
Catherine
  



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