st: Calculating proportional growth rate in stata and do-it files

[Georgia LockwoodEstrin <georgiale@googlemail.com>]

Hello there,
I have been trying to calculate the proportional/relative growth rate (rate
of brain growth with age) - to do this i have:
1. logged the dependent variable (I.e. brain growth)
2. regressed against age (and another independent variable).
3. predicted yhat (predicted y values)
4. tabstat yhat, by(age) - to get the yhat values for x1 and x2 (formula
below)
4. put yhat values into the equation below to get proportional rate of
growth

% proportional growth rate = ((yhat x2 - yhat x1)/ (x2-x1)) * 100
where x2 is oldest age and x1 is youngest age

However, i am wondering if this is the most efficient way to calculate the
proportional rate of growth - as I have a lot of these rates of growth to
get through, and it seems very  long way of calculating it? Perhaps it is
possible to put this all into a do -it file? in which case how to i program
stata to do the above calculated for each of my different variables?

Thanks!
Georgia
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