/* ex6_6.do

   example 6.6: figure 6.5

     (generate and save coordinate data for graphics pkg import)

   data required: dp2.dta
      Stover/Gorga DPOAE test data

   last update:  23 Apr 2003

*/
version 7
set more off
cap semt_profile
cap log close
pause on
set textsize 125

log using ${semt_log}ex6_6,replace
use ${semt_data}dp2,clear

replace y=-y
gen xl=l/10
gen xf=f/100
gen xd=(amt-20)/10 if d==1
sort d
by d:summ x* y

regress y xf xl if d==0
pause q <return> to continue . . .
predict rhat0 if d==0,rstandard

regress y xf xl xd if d==1
predict rhat1 if d==1,rstandard
gen res=rhat1 if d==1
replace res=rhat0 if d==0

* std normal cdf of residuals:
gen sncdf = norm(res)

* empirical cdf of residuals:
cumul res, gen(ecdf)

/* normal probability plot a la pnorm: */
pnorm res,grid saving(${semt_log}figure6_5,replace)

pause q <return> to continue . . .
/* save sncdf & ecdf for normal probability plot */
sort ecdf
#delimit ;
gr sncdf ecdf ecdf, s(.i) c(.l)
  xscale(0,1) yscale(0,1)
  xlab(0(.25)1) ylab(0(.25)1)
  xline(0(.25)1) yline(0(.25)1)
;
#delimit cr
keep sncdf ecdf
order ecdf sncdf
sort ecdf
save ${semt_log}fig6_5,replace
qui log close