[R] stepAIC invalid scope argument

[Prof Brian Ripley]

In case it is unclear why in this case there is a problem: you are running 
a function (here model.frame) in the stats namespace and so it looks in 
the stats namespace before the workspace when looking for 'df'.

On Mon, 15 Aug 2005, Prof Brian Ripley wrote:

> Try not to use the name of an R object ... the error is caused by using
> 'df' as the second argument to eval().
>
> It works with DF in place of df.
>
> I don't understand your subject line: that is not the error message you
> received.
>
> On Mon, 15 Aug 2005, 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 argument
>>
>> Here is a traceback of the first failed command :
>> 14: eval(predvars, data, env)
>> 13: model.frame.default(formula = y ~ x2 + x3 + x1, data = df, drop.unused.levels = TRUE)
>> 12: model.frame(formula = y ~ x2 + x3 + x1, data = df, drop.unused.levels = TRUE)
>> 11: eval(expr, envir, enclos)
>> 10: eval(mf, parent.frame())
>> 9: lm(formula = y ~ x2 + x3 + x1, data = df, method = "model.frame")
>> 8: eval(expr, envir, enclos)
>> 7: eval(fcall, env, parent.frame())
>> 6: model.frame.lm(fob, xlev = object$xlevels)
>> 5: model.frame(fob, xlev = object$xlevels)
>> 4: stats:::add1.lm(object, scope = scope, scale = scale)
>> 3: addterm.lm(fit, scope$add, scale = scale, trace = max(0, trace - 1), k = k, ...)
>> 2: addterm(fit, scope$add, scale = scale, trace = max(0, trace - 1), k = k, ...)
>> 1: stepAIC(mid, scope = list(upper = ~x1 + x2 + x3, lower = ~1))
>>
>> Any pointers would be much appreciated. Thank you.
>>
>> Regards, Adai
>>
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>>
>
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595