R help - Oct 2010 - How to extract parameter estimates of variance function from lme fit

Dear R-Users,

I have a question concerning extraction of parameter estimates of 
variance function from lme fit.

To fit my simulated data, we use varConstPower ( constant plus power 
variance function).
fm<-lme(UPDRS~time,data=data.simula,random=~time,method="ML",weights=varConstPower(fixed=list(power=1)))
I extract the results of this function by using the following codes:
y<-summary(fm)
x<-y$modelStruct$varStruct
 > x
Variance function structure of class varConstPower representing
        const        power
1.184535e-15 1.000000e+00

These are the constants and power that apppear in the summary(fm), and 
that I want to extract.
Hower I got different value of const when extracting from x:

 > x$const
     const
-34.36943

Does anyone know why there is such difference and how to extract the 
expected value (1.184535e-15) ?

Thanks in advance for your help.

Thu


---

THAI Hoai Thu
INSERM U738 - Universit? Paris 7
16 rue Henri Huchard
75018 Paris, FRANCE
Tel: 01 57 27 75 39
Email: hoai-thu.thai at inserm.fr

Try this:

coef(fm$modelStruct$varStruct, uncons = FALSE)

On Fri, Oct 15, 2010 at 11:42 AM, Hoai Thu Thai
<hoai-thu.thai@inserm.fr>wrote:
> Dear R-Users,
>
> I have a question concerning extraction of parameter estimates of variance
> function from lme fit.
>
> To fit my simulated data, we use varConstPower ( constant plus power
> variance function).
>
>
fm<-lme(UPDRS~time,data=data.simula,random=~time,method="ML",weights=varConstPower(fixed=list(power=1)))
> I extract the results of this function by using the following codes:
> y<-summary(fm)
> x<-y$modelStruct$varStruct
> > x
> Variance function structure of class varConstPower representing
>       const        power
> 1.184535e-15 1.000000e+00
>
> These are the constants and power that apppear in the summary(fm), and that
> I want to extract.
> Hower I got different value of const when extracting from x:
>
> > x$const
>    const
> -34.36943
>
> Does anyone know why there is such difference and how to extract the
> expected value (1.184535e-15) ?
>
> Thanks in advance for your help.
>
> Thu
>
>
> ---
>
> THAI Hoai Thu
> INSERM U738 - Université Paris 7
> 16 rue Henri Huchard
> 75018 Paris, FRANCE
> Tel: 01 57 27 75 39
> Email: hoai-thu.thai@inserm.fr
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

	[[alternative HTML version deleted]]

Thank you Henrique!! It works.

Thu


Le 15/10/2010 16:53, Henrique Dallazuanna a ?crit :
> coef(fm$modelStruct$varStruct, uncons = FALSE)