Trace:
A sequence of points.
A trace is a 2D drawing element that displays a sequence of points at given coordinates of the parent drawing or plotting panel. The points to be displayed are added sequentially, one after the other, and can be visualized using markers or connecting them with segments (or both).
The trace can be instructed to display a maximum number of points, in which case, it will discard old values to accomodate new ones. However, if the property No Repeat is set to true, and the new value is identical to the last one, this new value will be ignored. The reception of data can also be (usually temporarily) disabled. Finally, the trace can be instructed to accept only one out of a certain number of points received. This is useful in case the model generates too many data points.
Traces can have memory. This means that they can remember and display data that was generated in a previous run of the simulation. This can be very useful to allow the user to compare diferent trajectories for different initial values of a system. The number of data sets a trace can display, the way it displays them and the color it uses are governed by the memory properties. Data in memory is respected by a call to _initialize() or _view.resetTraces(), but is lost by a call to _reset() or _resetView().
Traces respond to user interaction on their position coordinates (which can be different to the coordinates of the points received), changing their position and invoking up to five different actions. Right-clicking on a trace brings in a window with a table of all input points currently displayed.