AR(2) model in streamtools

ar2.json

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Every second the log will create the next value of the AR(2) process. The pattern operates through 2 delays - one creates a sample delayed by one second and the other creates a sample delayed by 2 seconds. These are then weighted and summed, before triggering a draw from the normal distribution. Each output is fed back into the delays.

Note that both delays should be initialised ( TODO: in fact it's slightly unclear what is being simulated if only the first is initialised).