[R] What is the effect of how.many in the "contrast" function

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Fri Feb 14 14:52:42 CET 2014

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Sent from my phone. Please excuse my brevity.

On February 13, 2014 11:04:46 PM PST, jimj <jimj at sfu.ca> wrote:
>Thanks Dr. I did read the help page but maybe I just don't understand
>about contrasts to take what I need from it. It says:
>"If value supplies more than how.many contrasts, the first how.many are
>used. If too few are supplied, a suitable contrast matrix is created by
>extending value after ensuring its columns are contrasts (orthogonal to
>constant term) and not collinear."
>I suppose what this means is that if the matrix is not extended then
>is some type of problem with orthogonality? Perhaps my real question
>be, why is a contrast matrix with only one column not suitable. 
>Maybe I should read the book you are referring to. Can you provide a
>reference? Thanks!
>View this message in context:
>Sent from the R help mailing list archive at Nabble.com.
>R-help at r-project.org mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

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