set.seed(618)
m = 1000;  x = numeric(m);  x[1] = 0
for (i in 2:m)
  {
  if (x[i-1] == 0) x[i] = rbinom(1,1,.9)
  else             x[i] = rbinom(1,1,.2)
  }
table(x)
x
  0   1
458 542

par(mfrow=c(1,3))
 plot(x[1:30], type="b", pch=19)
 acf(x)
 acf(diff(x))
par(mfrow=c(1,1))