This is a read-only property which is maintained for you by RainPro to allow you to use the ‘modelfit’ style and then make use of the formatted equation.

eqn„ch.Query 'equation'

The result will be a simple string, probably formatted using the supplied template. It could be used in a chart note to give the reader details of the equation used. This property is always maintained, even if the ‘annotate’ style has not been used.

See also ...
EquationFormat – template for modelfit equation
Modelfit