R help - Sep 2011 - Model Selection with Phylogenetic Independent Contrasts

I'm trying to select a model under PCA using independent contrasts. Since
PICs need to be forced through the origin I've been using lmorigin for the
original regression, but it doesn't appear that stepAIC recognizes it. I
keep receiving an error message - "Error in na.fail.default(list(Phenology
c(NA_integer_, NA_integer_,  :
  missing values in object"

I'm having trouble navigating around this error message, and any suggestions
would be appreciated. 

Thanks!
Rose 

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rjswift <rosejswift <at> gmail.com> writes:
> 
> I'm trying to select a model under PCA using independent contrasts.
Since
> PICs need to be forced through the origin I've been using lmorigin for
the
> original regression, but it doesn't appear that stepAIC recognizes it.
I
> keep receiving an error message - "Error in
na.fail.default(list(Phenology > c(NA_integer_, NA_integer_,  :
>   missing values in object"
> 
> I'm having trouble navigating around this error message, and any
suggestions
> would be appreciated. 
>
  Do you mean "select a model under PIC"?  
  I think you'll be better off posting this to the r-sig-phylo at
r-project.org
mailing list.

  lmorigin() [which is in the ape package] is a special-purpose function;
the tricky part about fitting regressions through the origin is not
fitting them (adding a -1 or a +0 to a model formula does that easily)]
but making inferences about the resulting model.

  Depending on how you want to proceed, you can:

 1. examine the permutation p-values produced by lmorigin() and
do your stepwise procedure by hand;
 2. fit through the origin using lm(y~...-1,...) and use stepAIC
as usual

  However, I'm not sure which of this will be *correct* -- you're likely
to get wiser comments on r-sig-phylo.  In any case, beware stepwise
fitting approaches!