AR(2) stationary condition

phi1 <- seq(-3,3,0.1)

phi2<-seq(-3,3,0.1)

phi <- merge(phi1,phi2)

flag<-rep(0,3721)

for(i in 1:3721){

z=polyroot(c(1, -phi$x[i],-phi$y[i]))

az=abs(z)

flag[i]=ifelse((az[1]>1 & az[2]>1),1,0)

c<-cbind(phi,flag)

plot(c$x,c$y,col=c$flag)