Suggestion for using "trace" GUI element:
1. Set [b]Max Points[/b] to a fixed number:  for example: I normally define npt=300, then assign Max Points=npt , otherwise it will record all data points (it possible to use all computer memory).
2. set "[b]Memory[/b]" to 3 will keep the last 3 trace triggered by _initialize() . i.e. when _initialize() is execute a new trace is drawn.
3. If "[b]Mem Color[/b]" is assigned and different from "[b]Line color[/b]" , previous traces will change color to [b]Mem Color[/b].