[R] forcing a zero level in contr.sum

David Winsemius
2010-07-07T19:43:39Z

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.