[R] forcing a zero level in contr.sum

David Winsemius dwinsemius at comcast.net
Wed Jul 7 21:43:39 CEST 2010

On Jul 7, 2010, at 3:13 PM, Bond, Stephen wrote:

> I need to use contr.sum and observe that some levels are not  
> statistically different from the overall mean of zero.
> What is the proper way of forcing the zero estimate? It seems the  
> column corresponding to that level should become a column of zeros.
> Is there a way to achieve that without me constructing the design  
> matrix?
> Thank you.

lm( formula = z ~ x + y + 0,   ...)  _might_ do something close to  
what you want.

David Winsemius, MD
West Hartford, CT

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