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thanks gareth

i have done first differencing and seasonal first differencing on my data. i have selected my best model for my first difference data and also selected a model for my seasonal first differenced data. i have used the models to forecast for a 4 month outside my range.

my question is how do i covert the forecast values from my models to comparable figures like my original data. because they only forecast differences for the 4 months because i differenced the data.

thanks gareth

i have done first differencing and seasonal first differencing on my data. i have selected my best model for my first difference data and also selected a model for my seasonal first differenced data. i have used the models to forecast for a 4 month period outside my range.

my question is how do i covert the forecast values from my models to comparable figures like my original data because the models only forecasted differences for the 4 month period since my data was differenced.

If you estimate your model with the differenced expression instead of a series generated from the differenced expression, the forecast procedure will give you the option of forecasting the original level. The docs have details.