[R] Factor deletion criteria

David Winsemius dwinsemius at comcast.net
Sat May 4 05:47:30 CEST 2013

On May 3, 2013, at 3:32 PM, Iuri Gavronski wrote:

> Hi,
> I would like to know the criteria by which R removes a factor in linear
> models. For example, I have a four level factor, and R creates 3 dummies to
> estimate coefficients. Which level is chosen? Can I chance it?

The default order is alphabetical. Lowest lexical sorted item is the reference level.

Changing levels is possible:


David Winsemius
Alameda, CA, USA

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