cigmales <- cigmales %>%
mutate(age2 = age ^ 2, educ2 = educ ^ 2,
age3 = age ^ 3, educ3 = educ ^ 3,
educage = educ * age)
gmm_cig <- expreg(cigarettes ~ habit + price + restaurant + income + age + age2 +
educ + educ2 + famsize + race | . - habit + age3 + educ3 +
educage + lagprice + reslgth, data = cigmales,
twosteps = FALSE)
sargan(gmm_cig)
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