: 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
/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
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 *
# 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,
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
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
6 matches
Mail list logo