/* fig6_8.do

   figure 6.8 (example 6.12)

   parameter estimates from example 6.12 (ex6_12.do)
   radiology reading study data (Muller)
   ROC based on ROC-GLM fit of ordinal regression model

   updated 05/01/03

*/
version 7
set more off
cap semt_profile
cap log close
**********************************************
local alpha_0 = 1.561
local alpha_1 = 0.708
local  beta_1 = 0.441

drop _all
range t 0 1 500

* x is indicator for modality B (0 = modality A)

foreach x in 0 1 {
    gen v = `alpha_0' + `alpha_1'*ln(t/(1-t)) + `beta_1'*`x'
    gen roc`x' = exp(v)/(1 + exp(v))
    drop v
    recode roc`x' . = 0 if t==0
    recode roc`x' . = 1 if t==1
}

sort t
gen forty5 = t if t==0 | t==1

sort t roc*
gr roc* forty5 t, s(...) c(lll)
keep t roc* forty5
sort t roc*
save ${semt_log}fig6_8, replace