From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>

Date: Tue 16 Aug 2005 - 01:33:22 EST

Date: Tue 16 Aug 2005 - 01:33:22 EST

On Mon, 15 Aug 2005, Adaikalavan Ramasamy wrote:

> You are right, it works fine with a different name. Its a bad habit that

*> I need to shake off.
**>
**> The error message said that the second argument was invalid. The second
**> argument in stepAIC and addterm is 'scope' and thus the title.
*

OK, we'll improve the error message ....

*>
*

> Thank you again.

*>
**> Regards, Adai
**>
**>
**>
**> On Mon, 2005-08-15 at 15:23 +0100, 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
**>>>
**>>> ______________________________________________
**>>> R-help@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@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@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.htmlReceived on Tue Aug 16 01:42:49 2005

*
This archive was generated by hypermail 2.1.8
: Sun 23 Oct 2005 - 15:20:06 EST
*