leasqr with two variables

[Edvard Aasen]

Hi

 

Im looking for a program that can find parameters in an equation with two independent variables (X1 and X2) and experimental data Y. The equation is

 

Y = p1 + p2*X1 + (p3+ p4*X1) / X2

 

X2 is temperature, X1 is molecular weight and Y is logaritm of viscosity

I have good start-values for the parameters

I have used leasqr for 1 variable but dont know how to expand it to two parameters

 

I have done something similar in matlab (lsqcurvefit) some years ago but i dont have access to malab today. Thanks for any ansvers