My basic cross-sectional (countrywise) model is based on regress life_exp gdp_pc_ppp sq_gdp_pc_ppp
Now, I have put each country into one of 5 regions (continents) and generated dummy variables for 4 of them (leaving one as base).
Next, I need to add an interaction term in order to see whether the life_exp depends on gdp_pc_ppp in a different way in africa than others.
A bit lost on how to introduce the interaction term in this situation...