Call:arima(x = y, order = c(0, 1, 1), seasonal = list(order = c(0, 1, 1), period = 12),     xreg = x, include.mean = F)Coefficients:          ma1     sma1       x      -0.6341  -0.3722  0.8496s.e.   0.1421   0.1371  0.0711sigma^2 estimated as 0.001733:  log likelihood = 123.8,  aic = -239.6
arima的结果怎么写表达式