I'm have a time series that is dependent on a large number of other timeseries, but these dependent timeseries don't add up to the main one, as I don't have the full population of these dependent timeseries, only a sample.
All of these dependent time series are likely to be different and they are unlikely to be randomly sampled from the population.
I was thinking of forming a linear combination of these dependent timeseries to try and then use chi-sq minimisation to find the values of the co-efficients.
As the superposition could have about 60 coefficients (timeseries), I think the problem could be quite degenerate.
My question is: does this sound reasonable, and what problems am I likely to run into, or is there a more powerful way of doing this?