Re: [R] nls convergence trouble

: r-help@r-project.org Objet : Odp: [R] nls convergence trouble Hi Excel fit is not exceptionally good. Try fff-function(a,b) (V + b * m * a + C0 * V * b - ((C0 * V * b)^2 + 2 * C0 * + b * V^2 - 2 * C0 * V * m * a * b^2 + V^2 + 2 * V * m * a * + b + (b * m * a)^2)^(1/2))/(2 * b * m

Re: [R] nls convergence trouble

/Cordialement Benoit Boulinguiez -Message d'origine- De : Petr PIKAL [mailto:[EMAIL PROTECTED] Envoyé : mercredi 3 septembre 2008 17:58 À : Benoit Boulinguiez Cc : r-help@r-project.org Objet : Odp: [R] nls convergence trouble Hi Excel fit is not exceptionally good. Try

Re: [R] nls convergence trouble

Hi Benoit, another way of making Petr's point is by looking at the profile log likelihood function for b; that is, only estimating the a parameter for a grid of b values: ## Defining mean function for fixed b lgma - function(b){ function(C0, m, V, a){ (V + b * m * a + C0 * V * b - ((C0 *

Re: [R] nls convergence trouble

# 1. Supplying the derivatives results in convergence: lgmg - function(a, b, C0, m, V) { + e - expression((V + b * m * a + C0 * V * b - ((C0 * V * b)^2 + 2 * + C0 * b * V^2 - 2 * C0 * V * m * a * b^2 + V^2 + 2 * V * m * + a * b + (b * m * a)^2))/(2 * b * m)) + val - eval(e) + attr(val,

[R] nls convergence trouble

Hi, Parameters assessment in R with nls doesn't work, though it works fine with MS Excel with the internal solver :( I use nls in R to determine two parameters (a,b) from experimental data. m VC0 CeQe 1 0.0911 0.0021740 3987.581 27.11637

Re: [R] nls convergence trouble

Try squaring both sides of the formula. On Wed, Sep 3, 2008 at 10:01 AM, Benoit Boulinguiez [EMAIL PROTECTED] wrote: Hi, Parameters assessment in R with nls doesn't work, though it works fine with MS Excel with the internal solver :( I use nls in R to determine two parameters (a,b) from