You appear to be doing the differencing twice. Do it only in arima, and
not in the data you supply.
On Thu, 15 May 2008, Habib, Mohamed A F A M wrote:
> I have the following model:
>
>
m1.dis=arima(diff(diff(log(ts1),lag=12)),order=c(0,1,1),seasonal=list(order=c(0,1,1),period=12))
>
> I would like to know how to plot the correct predictions in the original
> units because I am trying the following code but it is not working.
For some value of 'not working' unknwon to us. Please see the footer to
this (and very) message.
> I believe that there must be something to account for the differencing.
>
>
plot(m1.dis,n1=c(1990,1),n.ahead=36,xlab='Year',type='o',ylab='Discharge
(cfs)',transform=exp)
>
>
> [[alternative HTML version deleted]]
>
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--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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