* Stata simulation

clear all
set cformat %9.2f
set obs 1000000
gen X     = runiformint(0,1)
gen male  = runiformint(0,1)
gen gop   = runiformint(0,1)
gen     Y =  -1*X if male==0 & gop==0 // non-male non-GOP
replace Y =  -3*X if male==1 & gop==0 //     male non-GOP
replace Y =  -6*X if male==0 & gop==1 // non-male     GOP
replace Y = -20*X if male==1 & gop==1 //     male     GOP

reg Y X male gop
reg Y c.X##i.male c.X##i.gop

gen Xmale= X*male
gen Xgop = X*gop
reg Y X male gop Xmale Xgop

# R simulation

rm(Y, X, male, gop)
options(scipen=999)

sample.size         <- 1000000
X                   <- runif(sample.size, 0:1)
male                <- sample(0:1, sample.size, replace=T)
gop                 <- sample(0:1, sample.size, replace=T)
Y                   <- NA
Y[male==0 & gop==0] <-  -1*X[male==0 & gop==0]
Y[male==1 & gop==0] <-  -3*X[male==1 & gop==0]
Y[male==0 & gop==1] <-  -6*X[male==0 & gop==1]
Y[male==1 & gop==1] <- -20*X[male==1 & gop==1]

summary(lm(Y ~ X*male + X*gop))