Fit Curve Options

Fit Curve Model Formulas provides the formulas for the models on the Fit Curve red triangle menu.

Fit Curve Model Formulas
Model	Formula
Polynomials	where k is the order of the polynomial. These models can also be fit using the Fit Model and Fit Y by X platforms.
Logistic 2P	a = Growth Rate b = Inflection Point Available only when all response values are between zero and one.
Logistic 3P	a = Growth Rate b = Inflection Point c = Asymptote
Logistic 4P	a = Growth Rate b = Inflection Point c = Lower Asymptote d = Upper Asymptote
Logistic 4P Rodbard	a = Growth Rate b = Inflection Point c = Lower Asymptote d = Upper Asymptote Available only when the regressor values are positive.
Logistic 4P Hill	a = Growth Rate b = Inflection Point c = Lower Asymptote d = Upper Asymptote
Logistic 5P	a = Growth Rate b = Inflection Point c = Asymptote 1 d = Asymptote 2 f = Power
Probit 2P	a = Growth Rate b = Inflection Point Φ = Normal Distribution CDF Available only when all response values are between zero and one.
Probit 4P	a = Growth Rate b = Inflection Point c = Asymptote 1 d = Asymptote 2 Φ = Normal Distribution CDF
Gompertz 3P	a = Asymptote b = Growth Rate c = Inflection Point
Gompertz 4P	a = Lower Asymptote b = Upper Asymptote c = Growth Rate d = Inflection Point
Exponential 2P	a = Scale b = Growth Rate
Exponential 3P	a = Asymptote b = Scale c = Growth Rate
Biexponential 4P	a = Scale 1 b = Decay Rate 1 c = Scale 2 d = Decay Rate 2 Available only when the response values are positive.
Biexponential 5P	a = Asymptote b = Scale 1 c = Decay Rate 1 d = Scale 2 f = Decay Rate 2
Mechanistic Growth	a = Asymptote b = Scale c = Growth Rate
Gaussian Peak	a = Peak Value b = Critical Point c = Growth Rate
Lorentzian Peak	a = Peak Value b = Growth Rate c = Critical Point
One Compartment Oral Dose	a = Area Under Curve b = Elimination Rate c = Absorption Rate Available only when the response values and the regressor values are all positive.
Two Compartment IV Bolus Dose	α = β = a = Initial Concentration b = Transfer Rate In c = Transfer Rate Out d = Elimination Rate Available only when the response values and the regressor values are all positive.
Michaelis-Menten	a = Max Reaction Rate b = Inverse Affinity Available only when the response values and the regressor values are all positive.