ey
Sent: Monday, August 11, 2008 11:34 PM
To: Nazareno Andrade
Cc: r-help
Subject: Re: [R] No answer in anova.nls
The reason for no F test showing up is that the additional df is 0 and the
F value is Inf. But the underlying problem is that your models are not
nested and so ANOVA between them is invalid
You can compare non-nested nls fits using the AIC command. Although
that does not give a formal hypothesis test there are rules of thumb for
using the AIC.
On Tue, Aug 12, 2008 at 2:13 AM, Nazareno Andrade
<[EMAIL PROTECTED]> wrote:
> Dear R-helpers,
>
> I am trying to check whether a model of the
>
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> On
> Behalf Of Prof Brian Ripley
> Sent: Monday, August 11, 2008 11:34 PM
> To: Nazareno Andrade
> Cc: r-help
> Subject: Re: [R] No answer in anova.nls
>
> The reason for no F tes
ither.
-- Bert Gunter
Genentech
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Prof Brian Ripley
Sent: Monday, August 11, 2008 11:34 PM
To: Nazareno Andrade
Cc: r-help
Subject: Re: [R] No answer in anova.nls
The reason for no F test showing up is tha
ad you to choose one or the other of your models -- or neither.
>
> -- Bert Gunter
> Genentech
>
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Prof Brian Ripley
> Sent: Monday, August 11, 2008 11:34 PM
> To: Nazareno An
The reason for no F test showing up is that the additional df is 0 and the
F value is Inf. But the underlying problem is that your models are not
nested and so ANOVA between them is invalid.
I suggest you seek help from a local statistician: your misunderstanding
and your question about model
Dear R-helpers,
I am trying to check whether a model of the form y(t) = a/(1 +b*t) fits the
curve of downloads per day of a file in a specific online community better
than a model of the form y(t) = a*exp(-b*t). For that, I used nls to fit
both models and I am now trying to compare the fits with a
Dear R-helpers,
I am trying to check whether a model of the form y(t) = a/(1 +b*t) fits the
curve of downloads per day of a file in a specific online community better
than a model of the form y(t) = a*exp(-b*t). For that, I used nls to fit
both models and I am now trying to compare the fits with a
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