Re: [R] curve fitting problem

2007-12-24 Thread Gabor Grothendieck
Your model is singular. Varying m and log(l) have the same effect: log(ir) = log(k) + m * log(l) * ox Also with plinear you don't specify the linear coefficients but rather an X matrix whose coefficients represent them: If we use this model instead: ir = k * exp(m * ox) Then: > mod0 <- lm(log(

[R] curve fitting problem

2007-12-24 Thread pieterprovoost
I'm trying to fit a function y=k*l^(m*x) to some data points, with reasonable starting value estimates (I think). I keep getting "singular matrix 'a' in solve". This is the code: ox <- c(-600,-300,-200,1,100,200) ir <- c(1,2.5,4,9,14,20) model <- nls(ir ~ k*l^(m*ox),start=list(k=10,l=3,m=0.004