nonlinear regression curve fitting

*To*: uiucuxc!yoda.ncsa.uiuc.edu!mathgroup*Subject*: nonlinear regression curve fitting*From*: Walter Vogel - Biochem <uiucuxc!bionette.CGRB.ORST.EDU!vogelw>*Date*: Tue, 7 Nov 89 13:58:09 PST

Does anyone know of a package to do nonlinear regression curve fit to a function, possibly using Marquardt's algorithm? I am interested in fitting data to an equation of the form y=f(y,x) or z=f(x,y). Below is the equation I wish to fit. The equation: _ _ | | [L] | F1 F2 | Y= ----- | ------------------- + ------------------- | K | 1 + [I]/K1 + [L]/K 1 + [I]/K2 + [L]/K | |_ _| There are 4 parameters to be determined: K, K1, K2, F1 (since F1 + F2 =1, F2 is not a parameter. Our raw data is obtained as radioactive counts versus the independent variable, [I]. The counts are used to calculate both Y and [L] thus our dependent variable appears on both sides of the equation. Y=(T-n)/r and [L]=q-T. As written above the equation is a function of two variables [I] and [L] but it can be recast as function of one T=f(T([I]),[I]). Sincerely Walter K. Vogel vogelw at bionette.cgrb.orst.edu