[R] Running a likelihood ratio test for a logit model

[Chris Bergstresser]

Hi all --

   I have to calculate a likelihood ratio test for a logit model.  I
found logLik, but I need to calculate the log likelihood for the model
without any predictors.  How can I specify this in glm?  If the full
model is glm(y ~ x1), is the one without predictors (y ~ 0)?  Or (y ~
1)?
   Is there a more direct way of getting this?

-- Chris