plot(forecast(na.omit(ar(transformed, order.max = 2)), h = 2), xlim = c(480, 510), ylim = c(2800, 3050), main = "", xlab = "Time", ylab = "USD")
lines(prices[, "GSPC.Close"], col = "red")
legend(502, 3025, legend = c("Signal", "Transformed", "Predicted"), col = c("red", "black", "blue"), lty = c(1, 1, NA), pch = c(NA, NA, 16))