set verbose off
open cps91.gdt --quiet

smpl inlf > 0 --restrict
exper2 = exper^2

# for parts 3 and 4
X1 = {1, 15, 5, 5^2, 0}
X2 = {1, 18, 20, 20^2, 1}

list xlist = educ exper exper2 union

ols hrwage const xlist
# for part 3
lin_pred1 = X1 * $coeff
# for part 4
lin_pred2 = X2 * $coeff

ols lwage const xlist
# for part 3
log_pred1 = exp($sigma^2/2)*exp(X1 * $coeff)
# for part 4
log_pred2 = exp($sigma^2/2)*exp(X2 * $coeff)

print "Comparison of predictions"
printf "Part 3: linear fit $%g, log fit $%g\n", lin_pred1, log_pred1
printf "Part 4: linear fit $%g, log fit $%g\n", lin_pred2, log_pred2

# augmented model
ols lwage const xlist black hispanic
omit black hispanic

# just black and hispanic
ols lwage const black hispanic
omit black hispanic