有关ARIMA的问题

> series=arima.sim(n=36,list(ma=-0.6))+100
> actual=window(series,start=33);series=window(series,end=32)
> model=arima(series,order=c(0,0,1));model

Call:
arima(x = series, order = c(0, 0, 1))

Coefficients:
          ma1  intercept
      -0.4626    99.9779
s.e.   0.1260     0.1052

sigma^2 estimated as 1.157:  log likelihood = -47.85,  aic = 101.71
> result=plot(model,n.head=4,ylabel="Series&Forecasts",col=NULL,pch=19)
错误于xy.coords(x, y, xlabel, ylabel, log) :
  'x' is a list, but does not have components 'x' and 'y'
请问最后一步应该怎么修改？

运行str(model)后发现里面有13个元素