[R] Non linear regression with 2 explanatory variables

[Rolf Turner]

I have never had much success in using nls().  If you scan the archives
you will find one or two postings from me on this topic.  I have  
received
no useful responses to these postings.

I have found that anything that I tried (and failed) to do using nls()
could be done quite easily using optim().

	cheers,

		Rolf Turner


On 17/01/2008, at 3:56 AM, Gavin Simpson wrote:

> hits=-2.6 tests=BAYES_00
> X-USF-Spam-Flag: NO
>
> On Wed, 2008-01-16 at 11:02 +0100, Janice Kielbassa wrote:
>> Hello!
>>
>> I want to do a non-linear regression with 2 explanatory variables
>> (something like : length ~ a * time * exp( b* temperature)), having a
>> data set (length, time, temperature). Which function could I use (I
>> tried nls but I think it doesn't work)
>
> Janice, I'll start by saying I can't help you as I have never used  
> nls()
> myself and I am not familiar with this type of analysis.
>
> Why do you think that nls() "doesn't work"? It is a widely used  
> part of
> R and thus probably very well tested.
>
> My understanding of these things is that nls is a sophisticated tool
> that requires some effort on the part of the user, such as selecting
> appropriate starting values.


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