Re: [R] stepAIC invalid scope argument

From: Adaikalavan Ramasamy <ramasamy_at_cancer.org.uk>
Date: Tue 16 Aug 2005 - 14:09:35 EST

Thank you. Your suggestion is equivalent is the same as my second stepAIC command that failed in R-2.1.1.

See Prof. Ripley's reply where he pointed out that this was due to using the name 'df' which clashes with built-in function with the same name from stats package.

Regards, Adai

On Tue, 2005-08-16 at 15:52 +0100, John Wilkinson (pipex) wrote:
> Adai,
>
> The following works.Perhaps you should define your 'upper' and 'lower'
> in the list as aov's, as you have done with your lo,hi and mid.
>
> John
>
> > stepAIC( mid, scope=list(upper = mid , lower = lo) )
> Start: AIC= -594.66
> y ~ x2 + x3
>
> Df Sum of Sq RSS AIC
> - x2 1 0.11 548.56 -596.45
> - x3 1 0.95 549.40 -594.93
> <none> 548.45 -594.66
>
> Step: AIC= -596.45
> y ~ x3
>
> Adaikalavan Ramasamy wrote ---
>
> I am trying to replicate the first example from stepAIC from the MASS
> package with my own dataset but am running into error. If someone can
> point where I have gone wrong, I would appreciate it very much.
>
> Here is an example :
>
> set.seed(1)
> df <- data.frame( x1=rnorm(1000), x2=rnorm(1000), x3=rnorm(1000) )
> df$y <- 0.5*df$x1 + rnorm(1000, mean=8, sd=0.5)
> # pairs(df); head(df)
>
> lo <- aov( y ~ 1, data=df )
> hi <- aov( y ~ .^2, data=df )
> mid <- aov( y ~ x2 + x3, data=df )
>
> Running any of the following commands
>
> stepAIC( mid, scope=list(upper = ~x1 + x2 + x3 , lower = ~1) )
> stepAIC( mid, scope=list(upper = hi , lower = lo) )
> addterm( mid, ~ x1 + x2 + x3 )
> addterm( lo, hi )
>
> gives the same error message :
> Error in eval(expr, envir, enclos) : invalid second argumen
>
>



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