# PS8.1, for Examples 8.1 and 8.2 
open data3-11
genr LNSALARY=ln(SALARY)
# Figure 8.2 and Example 8.1 
graph LNSALARY YEARS 
genr YRS2 = YEARS*YEARS
# estimate basic log quadratic model for Example 8.2 
ols LNSALARY const YEARS YRS2 
# save uhat squared and predicted LNSALARY 
genr usq=$uhat*$uhat
# genr predicted LNSALARY as actual minus residual stored as uhat 
genr yhat1=LNSALARY-$uhat
# graph estimated residual variance against YEARS and yhat 
graph usq YEARS 
graph usq yhat1 
