Generates data set of target event rates given a target data.
The data should already be scaled to the same length as the forecast time horizon. Explicit checks for these cases are not conducted in this function.
If scale=True then the target event rates will be scaled down to the rates for one day. This choice of time can be made without a loss of generality. Please see Rhoades, D. A., D. Schorlemmer, M. C. Gerstenberger, A. Christophersen, J. D. Zechar, and M. Imoto (2011). Efficient testing of earthquake forecasting models, Acta Geophys 59 728-747.