*
*  Examples 19.1, 19.2
*  J. Wooldridge, Econometrics of Cross Section and Panel Data
*
*  Note: The sample data files include all required data transformations.
*        However, in many cases we show how these data transformations would
*        be created in RATS from the basic data, as this is something you will
*        need to know how to do in practice.
*
open data fertil2.raw
data(format=free,org=columns) 1 4361 mnthborn yearborn age electric radio tv bicycle educ $
  ceb agefbrth children knowmeth usemeth monthfm yearfm agefm $
  idlnchld heduc agesq urban urb_educ spirit protest catholic $
  frsthalf educ0 evermarr educ7
*
set agesq = age**2
*
* OLS regression.
*
linreg children
# educ age agesq evermarr urban electric tv constant
*
* Poisson regression.
*
ddv(type=count,robusterrors) children / resids
# educ age agesq evermarr urban electric tv constant
*
* Example 19.2
* Test of exogeneity of educ.
* Do first stage regression for educ, using frsthalf as an instrument.
*
linreg educ / reduc
# frsthalf age agesq evermarr urban electric tv constant
*
ddv(type=count,robusterrors) children
# educ age agesq evermarr urban electric tv constant reduc