The simulator mode

SIGSPEC supports two different simulator modes.

1. The keyword sim:add runs the simulator in additive mode. The program keeps the original observable values and adds the synthetic values. For example, this function is useful to add synthetic noise to a given time series.
2. The keyword sim:replace forces the simulator to overwrite the original observable values with the synthetic values.
3. The keyword sim:off is used, if no simulator activity is desired. Since the simulator is deactivated by default, this keyword is redundant and only implemented for completeness.