[R] How to do global curve fitting in R

Jianling Fan fanjianling at gmail.com
Wed Sep 9 18:28:34 CEST 2015

Hi, Bert

Thanks for your reply.

I am fitting a logistic does response model with 3 parameters as :
y=a/(1+(x/x0)b), I have many sets of data. I can fit each of them for
the model. but I want them shared the parameter x0 and b, but varied
for each a.

I don't think it is a  statistics problem. It is a typical global
curve fitting problem with shared parameters. And I know how to do it
by many other software. But since I am trying to use R, I am wondering
is there any package or method to do it in R?



On 9 September 2015 at 10:16, Bert Gunter <bgunter.4567 at gmail.com> wrote:
> Jianling:
> 1. What models are you trying to fit? Details matter, and it is
> impossible to give a good answer without specifics.
> 2. In general terms, to do this one combines all the data and allows
> for "appropriate" changes in the model parameters for the different
> groups. For example, different intercepts, rate constants, etc. This
> is where the specifics matter.
> 3. This is really more a statistics than an R question, and you would
> probably do better to pursue these issues either with a local
> statistical resource or on a statistics site, like
> stats.stackexchange.com.
> Cheers,
> Bert
> Bert Gunter
> "Data is not information. Information is not knowledge. And knowledge
> is certainly not wisdom."
>    -- Clifford Stoll
> On Wed, Sep 9, 2015 at 9:04 AM, Jianling Fan <fanjianling at gmail.com> wrote:
>> Hello all,
>> I am trying to fit my data to a nls model. I have many sets of data
>> and each can fit well for the curve. but I want to fit them at once by
>> sharing 2 of 3 parameters of the model. I know it is a typical global
>> curve fitting problem, but I don't know how to do it by R?
>> Does anyone know any package for this??
>> Thanks a lot!
>> Julian
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Jianling Fan

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