Some functions should only be plotted between a range of X values.

Functions which return null throw exceptions and make rendering slow.

Public fields should be added so users can restrict function rendering to a range.

public double XMin = double.NegativeInfinity;
public double XMax = double.PositiveInfinity;

Then in the render function those values should be checked and rendering should be restricted to that range.

Presently the render function calculates X/Y pairs for every point from the full visible range of the plot:

This feature may resolve the issue described by @phil100vol in #2138