How to simulate and fit a ARIMA model like Y_t=Y_{t-1} + et in R

Question

This is my code but i don\'t know what\'s wrong with it (sad

e = numeric(1000)
e[1] <- rnorm(1)
for(i in 2:length(x))
  x[i] = 2 * x[i - 1] + rnorm(1)
x =