Yes this was one of the main reasons, plus average operator will give the average power, very important parameter if working with power devices. All these informations can be saved from ngspice directly in the raw file but:
• I always forget to do that. so if i need i have to re-run the simulation.
• I never remember the ngspice syntax to save a vector containing - say- the power (v * i) of a device.
For this reason, once i have the individual currents and voltages saved i want to be able to post-process the data to get these informations.