set verbose off
open housing.gdt

# create list of all variables ("dataset") besides price
list X = dataset - price

# run OLS
ols price const X

# predicted effect of central AC (the 10th coefficient)
AC_effect = $coeff[10]
printf "Predicted effect of AC on price: %g euro\n", AC_effect

# 95% CI for the above
se = $stderr[10]
lo = AC_effect - 2*se
hi = AC_effect + 2*se
printf "95 percent CI: %g to %g euro\n", lo, hi

# log-price version
logs price
ols l_price const X
# the AC effect is now (approximately) a percentage
AC_effect = $coeff[10]
printf "AC is predicted to add %g percent to price\n", 100*AC_effect

# focus on bedrooms as a factor in price
ols price const bedrooms

# The bedrooms coefficient here is much larger than in Model 1.
# Why? Because we're not controlling for a bunch of other features
# that are correlated with number of bedrooms