[R] nls: singular convergeance

[Redding, Matthew]

Hi Rolf and Others, 

Thanks Rolf for your suggestion.
I've had a look at segmented, but can't see how it can help.

My model is the solution to an ODE of a physical system. The fitted
parameters from 
this model are the answers I require. 

I'm not sure how segmented can help -- it is 
a linear regression tool. Can you let me know how it could be used?

Thanks, 

Matt Redding

>-----Original Message-----
>From: Rolf Turner [mailto:rolf.turner at xtra.co.nz] 
>Sent: Thursday, 13 October 2011 6:46 PM
>To: Redding, Matthew
>Cc: r-help at r-project.org
>Subject: Re: [R] nls: singular convergeance
>
>On 13/10/11 21:26, Redding, Matthew wrote:
>> Hi Rolf and others
>>
>> Will this make any difference to the convergence?
>     I have no idea, really.  I don't know if convergence issues even
>     arise in the context of the "segmented" package.  I have never
>     encountered any.
>
>     Try it and see.  Shouldn't take more than about 10 
>minutes, all up.
>
>         cheers,
>
>             Rolf
>> ----- Original Message -----
>> From: Rolf Turner<rolf.turner at xtra.co.nz>
>> To: Redding, Matthew
>> Cc: r-help at r-project.org<r-help at r-project.org>
>> Sent: Thu Oct 13 18:04:53 2011
>> Subject: Re: [R] nls: singular convergeance
>>
>> On 13/10/11 18:02, Redding, Matthew wrote:
>>> Dear R-experts,
>>>
>>> I have 28 data points that I would like to fit with a non linear 
>>> broken-stick -- with three fitted parameters.
>>> When I view trace -- and use the final values as lines on the graph 
>>> of data -- it looks pretty good.
>>>
>>> Q1. Why am I getting singular convergeance?
>>> Q2. Can you suggest another approach that may prove more satisfying?
>> <SNIP>
>>
>> Have you thought of using the "segmented" package instead of rolling 
>> your own with nls?
>>
>>       cheers,
>>
>>           Rolf Turner
>
>
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