I kindly ask if someone at this forum knows how to manually calculate the arma model using time series data. I know how to do this using Python and R but im in need to do this manually. The data would be volatile. For example: 3.375, 3.200, 3.160, 3.110, 3.105, 3.230, 3.295, 3.375, 3.445, 3.315, 3.675. So it would both increase and decrease.

How would I, by using the example data, build an ARMA forecast model?

Thanks in advance!