Sets the or returns the value used to generate the regression equation.
ArgumentExceptionThe value provided is not valid for the current Trendline.RegressionType value.
For Polynomial regression trendlines, the value will be the order of the polynomial. This value must be between 1-6, inclusive, with 1 representing a linear trendline.
For MovingAverage trendlines, the value specifies the number of periods over which the average is computed. This value must be greater than or equal to 2.
For all other regression types, this value is unused.