[R] test for a formulae

[Paulo J. Ribeiro Jr]

I'd like to check within a whether an argument is a formulae of the type
~X or similar.
What's the right way to do so?

I'm using: is.language(obj) but not sure this is right

Thanks in advance
P.J.

Paulo Justiniano Ribeiro Jr
Dept Maths & Stats  -  Fylde College
Lancaster University
Lancaster LA1 4YF   -  U.K.

e-mail: paulojus at est.ufpr.br
http://www.maths.lancs.ac.uk/~ribeiro






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