[R] Removing terms from formula

[McGehee, Robert]

R-help,
Given a simple linear model, say lm(x ~ y + z), I would like to remove
model terms that are factors with only one level. Thus, if 'z' were a
factor with only one level, lm(x ~ y + z) becomes lm(x ~ y + 1).
Likewise, if both 'y' and 'z' are one-level factors, then the resulting
calculation is simply lm(x ~ 1).

Unfortunately, I have not been able to come up with an elegant solution
to this. Any suggestions would be greatly appreciated.

Thanks,
Robert

Robert McGehee, CFA
Quantitative Analyst
Geode Capital Management, LLC
One Post Office Square, 28th Floor | Boston, MA | 02109
Tel: 617/392-8396    Fax:617/476-6389
mailto:robert.mcgehee at geodecapital.com



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