*
* Example 8.9 from page 282
*
open data gpa1.raw
data(format=free,org=columns) 1 141 age soph junior senior senior5 male campus business engineer $
 colgpa hsgpa act job19 job20 drive bike walk voluntr pc greek car siblings bgfriend clubs $
 skipped alcohol gradmi fathcoll mothcoll
*
* Generate PARCOLL (at least one parent attended college) from FATHCOLL and
* MOTHCOLL. This uses the .OR. operator, which evaluates to 1 if either FATHCOLL
* or MOTHCOLL is non-zero, and to zero if both are zero.
*
set parcoll = fathcoll.or.mothcoll
*
linreg pc
# constant hsgpa act parcoll
linreg(robust) pc
# constant hsgpa act parcoll
*
* Do LPM-specific correction for heteroskedasticity
*
prj predict
*
* Check to see what the range is on the predicted values
*
ext predict
*
* This is how you'd patch over values, if you needed to. It uses the
* %IF(condition,if true,if false) function; in fact, two of them nested.
*
set predict = %if(predict<0.0,.01,%if(predict>1.00,.99,predict))
*
linreg(spread=predict*(1-predict)) pc
# constant hsgpa act parcoll