Re: [R] How can I extract information from list which class is nls

From: Peter Ehlers <ehlers_at_ucalgary.ca>
Date: Tue, 26 Apr 2011 15:30:16 -0700

On 2011-04-26 15:11, Joshua Wiley wrote:
> Hi,
>
> One way would be:
>
> summary(nls.object)[["coefficients"]][, "Std. Error"]
>
> If you have a hankering to do it yourself rather than go through the
> summary formula, the code here will get you there:
> getAnywhere("summary.nls")
>
> If you are going to be doing it a lot, creating a little function might be nice:
>
> se.coef.nls<- function(model) {
> summary(model)[["coeffficients"]][, "Std. Error"]
> }
>
> se.coef.nls(yourmodel)
>
> I have been doing something along those lines for a number of models.
> Sadly, there is not a consistent name always given to the parameter or
> coefficients table, so it will not quite be one size fits all, but
> generally using str(), you can figure out what the names of what you
> want are so it is not much trouble to get out.

I would generally use the coef() extractor function if it's available (and it is for nls()). ?nls has an example:

   coef(summary(fm1DNase1))

which is a matrix from which you can get the SEs:

   coef(summary(fm1DNase1))[,"Std. Error"]

or

   coef(summary(fm1DNase1))[, 2]

Schatzi,
As to your other question about 'adding two parameters', that doesn't make sense to me. Can you provide a sensible example? In any case you would no doubt have to look at the covariance matrix of the parameter estimates (with vcov()).

Peter Ehlers

>
> str(summary(yourmodel))
>
> Cheers,
>
> Josh
>
> On Tue, Apr 26, 2011 at 11:21 AM, Schatzi<adele_thompson_at_cargill.com> wrote:
>> How do I extract the standard error of the parameter estimates?
>>
>> Also, if I would like to add two parameters together (x+y), can I use this
>> equation to calculate the new standard error?:
>> x = parameter 1
>> y = parameter 2
>> xSE = SE parameter 1
>> ySE = SE parameter 2
>>
>> NewSE=(x+y)*sqrt((xSE/x)^2+(ySE/y)^2)

>>
>>
>>
>> --
>> View this message in context: http://r.789695.n4.nabble.com/How-can-I-extract-information-from-list-which-class-is-nls-tp804151p3476154.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>>
>
>
>



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