Non-linear regression analysis in R
Could you provide the code that you're running, so we can see what you're trying to do? Even better would be a repeatable example. Jeremy
On 19 December 2012 09:42, Yann Labou <yann.labou at outlook.com> wrote:
Hey all, I'm trying to fit a non-linear model y ~ a * constant ^ b * x ^ c and estimates the paramaters a, b and c. Using the nls function, I'm getting following error message: Error in nlsModel(formula, mf, start, wts) : singular gradient matrix at initial parameter estimates If I logarithmize the whole equation log(y) ~ log (a) + b * log(constant) + c * log(x) and fit the equation with lm, I get only NAs estimates for the second term on the right side: Coefficients: (1 not defined because of singularities) Do you have any hints on how to fit this equation or any alternatives to nls? Thanks, Yann
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