
multiple variable exponential regression
Posted:
Nov 4, 2013 2:32 PM


Hello, I was using other nonlinear regression methods but was getting an imaginary solution (a+ib) form
I need to solve y = a0 + (a1*(x1^b1)) + (a2*(x2^b2)) + (a3*(x3^b3))
a0, a1, a2, a3 are known
I have data set for y, x1, x2, x3
I need to calculate b1, b2, b3
I was using following code till (this yields imaginary solutions)
opts = statset ('nlinfit'); opts.RobustWgtFun = 'bisquare'; beta0 = [0, 0, 0, 0]; modelfun = @(b, x)((100  15*(x(2, :).^b(1))))  (40*((x(3, :).^b(2))))  (15*((x(4, :).^b(3)))) x = TestData; y = x(1, :);
[beta, R, J, CovB, MSE] = nlinfit(x, y, modelfun, beta0, opts); SSresidual=sum(R.^2); SStotal =sum((ymean(y)).^2); rsquare =1(SSresidual/SStotal);

