I'm a student from Lithuania. I have found in one forum topic your discussion about non-linear equation convertion into a linear form.. I have some problem with that...Could you help me, please? :)

For, example, I have two non-linear models:

1. y = a [1/(1+b/(c+x))]*exp(-d*x)

2. y = a*exp[b*(1-exp(-c*x))/c - d*x]

And I want to convert it into linear equation, for fitting linear regression theory, of course, I could fit a newton or other method, but there are some problems with initial values. So, I would like to see the results of fitting to these models a linear regression and compare with iterative methods.

So, could you help me?

I think, that these two models linear form will be:

1. ln(y) = ln(a) - ln(1+b/(c+x)) - d*x + err

2. ln(y) = ln(a) + b(1-exp(-c*x))/c - d*x

lnln(y) = lnln(a) + ln(b/c)-ln(b/c)-c*x -ln(d) + ln(x)

the main problem is, how to estimate unknow a,b,c,d parameters...using for example, SAS programe package.

I would waiting from you any help.

With best regards, Ms. Dovile.