A nice feature would be to have equations on the display page.
This way you can create plots without running the simulator again if you decide you want to use phase or dB or something like that.
Implementation can be two ways:
-An extra mode is added to qucsator, to parse a dataset and apply some equations to it, this mode can be called if the schematic (.dpl) contains no simulation components
-A subset of the functions can be added to qucs, these functions can be added to the graph dialog and selected while adding a variable. I think this method is preferable from a user point of view because we don't have to run an external tool after an equation is added.