When you have an existing model, you may wish to remodel specific paths without overwriting others. You can use model masks to avoid 'flushing' the existing model coefficients that you wish to retain. In this manner, the Modelling Facilities only recomputes the model paths you have not masked out.
There are two mask types: section mask and signal mask. These are defined as follows:
- A section mask for any cause signal protects paths from that cause to ANY effect signal
- A section mask for an effect signal protects paths from ANY cause signal to that effect signal
- A signal mask protects the 'ARX' term - the path between that signal and its own previous value. Note the signal mask is not visible in the Modelling Facilities unless the order of the model is 1 or greater
When computing models that have masks configured, you must select 'No' when prompted to 'flush all coefficients' in your model. Selecting 'Yes' will flush all your coefficients.