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st: binary indicator for differing subsets of variables [SEC=UNCLASSIFIED]

From   "Fry, Jane" <[email protected]>
To   "'[email protected]'" <[email protected]>
Subject   st: binary indicator for differing subsets of variables [SEC=UNCLASSIFIED]
Date   Wed, 7 Sep 2011 14:04:50 +1000


I'm a bit new to data manipulation using Stata and I have a query: I'd like to set up an indicator variable based on the sum of the values in a selection of other variables.

So, in my dataset I have variables on individual characteristics (like birth month and year) and a series of binary variables on labour force status (in/out) for consecutive months and years from Aug 2006 - Jan 2010:
LFS0806 LFS0906 LFS1006 ... LFS1109 LFS1209 LFS0110.

I would like to create a binary indicator variable to show whether or not an individual is in the labour force for 6 consecutive months --
e.g. LFS0107, ... , LFS0607=1.
The tricky bit is that the 6 month window for each individual ends in the month when they turn 25 -- i.e. the window shifts according to birthday.

I have set up an 'initial date' identifier variable (date1) that tells me when to begin the window and a 'final date' identifier variable (date2) that tells me when to end the window. So date1 and date2 are string variables of the form "MMYY".

e.g. for the first observation, date1="0107" and date2="0607", so LFS0107 ... LFS0607 are relevant here.
        for the next observation, date1="0906" and date2="0307", so LFS0906 ... LFS0307 are relevant here.

I think what I need to do is generate a new variable X=.  and then replace its values (for each individual) with a 1 or 0 if the sum of the relevant LFS variables is 6.
i.e. the sum of LFSMMYY to LFS(MM+6)YY = 6 (or each LFS is 1).

Trouble is, I don't know how to do it. I thought something like an egen X = rowtotal("LFS"+date1 - "LFS"+date2) might work but I was wrong! Is there anyone who can help?

Many thanks,

Mrs. Jane Fry
Research Manager | Productivity Commission
12/530 Collins St, Melbourne
P: +61 3 9653 2125
E: [email protected]

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