On Dec 3, 2010, at 17:17 , S Ellison wrote:
> David,
>
> Thanks for the comments.
>
> I think, though, that I have found the answer to my own post.
>
>> Question: How would one check, in R, that [contrasts .. are
>> 'orthogonal in the row-basis of the model matrix'] for a particular
>> fitted
David,
Thanks for the comments.
I think, though, that I have found the answer to my own post.
>Question: How would one check, in R, that [contrasts .. are
>'orthogonal in the row-basis of the model matrix'] for a particular
>fitted linear model object?
?lm illustrates the use of crossprod() fo
There's a pretty good section in the R book by Crawley on contrast
statements in R, including some discussion of the contrasts being
orthogonal.
I would say you should just make your own table and sort it out there- if
you have equal sample sizes, then the contrast coefficients along the row
shoul
Hi Steve,
The short answer is that there is typically no reason to check (beyond
looking to see what contrasts have been defined for the factors in the
model; see ?contrasts) because the rules are pretty simple.
1) the design matrix is orthogonal on the row-basis (i.e., the columns
sum to zero) whe
A common point made in discussion of contrasts, type I, II, III SS etc
is that for sensible comparisons one should use contrasts that are
'orthogonal in the row-basis of the model matrix' (to quote from
http://finzi.psych.upenn.edu/R/Rhelp02/archive/111550.html)
Question: How would one check, in
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