[R] test for a formulae

[Prof Brian D Ripley]

On Fri, 2 Jun 2000, Paulo J. Ribeiro Jr wrote:

> 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

That allows lots of other things.

Formulae have class "formula", so inherits(obj, "formula") looks best.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._