Forecasting using ARIMA after series has been transformed


#1

Hi,
I have transformed my series using log and diff to make it stationary and now I want to forecast using the model but the otuput is coming as transformed i.e. original series was like 10000 and forecast is coming like 0.1 How to transform back into the original series so I can get the forecasted values in thousands.
Spareseries is my timeseries whcih consist numbers ranging between 10k and 15k
Code :
Spareseries2<-diff(log(Spareseries),12)
plot(Spareseries)
plot(Spareseries2)
Spare2 <- auto.arima(Spareseries2,trace=TRUE,test=“kpss”,ic=“aic”)
summary(Spare2)
confint(Spare2)
Spare_forecast2<-forecast(Spare2,h=3)