# PS6.4, for Practice Problems 6.5 and 6.6 of Section 6.4 
open data4-1
genr sqft2=sqft*sqft
# obtain logarithm of sqft 
genr lsqft=log(sqft)
# Practice problem 6.5 
ols price 0 sqft sqft2
# Practice problem 6.5 
ols price 0 lsqft
# Practice problem 6.6 
ols price 0 lsqft baths