*
* Example from section 7.4 beginning page 183
*
open data pizza.dat
data(format=free,org=columns) 1 40 pizza x2 x3 x4 x5 income age
*
linreg pizza
# constant age income
*
set age_income = age*income
*
linreg pizza
# constant age income age_income
*
disp "Marginal Effect of Age at Income=25000" %beta(2)+%beta(4)*25000
disp "Marginal Effect of Age at Income=90000" %beta(2)+%beta(4)*90000