Forecasting expected_spend_days about robyn

[gufengzhou]

Sorry for the late reply. The latest version has allocator scenario of "max_response" and "target_efficiency". See ?robyn_allocator for more description.

Robyn doesn't offer future forecasting, so you're right that the allocator is doing past simulation. But to be honest the only difference between forecast and simulation is the forecast of trend/ season etc. For media variables, the optimised budget is derived exactly the same as the past simulation, based on the same saturation curve and same coefficient. And of course the trend forecast is a task by itself anyways.

We're aware that many have asked for the forecast feature. We'll consider it in the future.