PID controller

[NuSynth]

I am only putting this issue here for myself, as a note. This is something that I want to implement with no help. I want to make certain that it is correctly done, and the only way for me to do that, is to understand how to write it. So, I may as well just write it.

Here is the idea for an enhancement:

A proportional–integral–derivative controller might be useful to adjust the interval spacing, after missing any number of study sessions. This should decrease the numerical value, for the variable where the difficulty calculation first stores it's output as well.

I don't know how this would yet work. But, the program needs this, or something like this, because some people are too busy on some of the days that the program will schedule repetitions on.

I've known that this would be a problem, if the program is not used for the days that are scheduled, before I even wrote this program. Earlier, I was looking for information on PID's, and found this article by accident:

https://en.wikipedia.org/wiki/PID_controller

I haven't done the math, and I may have mistaken how this system works. But I think that it may apply.

Since this program's scheduling actually works well, this update is not at the top of the priorities for the updates. First I want to add the course adding functionality, and then make any adjustments that may be needed, on the output values for the calculation of difficulty. After those two things, then this will be a priority of mine.