Use formula() on a data.frame object

USAGE:

formula.data.frame(object) 

This is a method for the function formula() for objects inheriting from class data.frame. If object is a model frame, the formula for the model frame is returned, otherwise a formula is deduced from the names of object. The first name is taken to be the response, and all the remaining names are pasted together additively.

EXAMPLES:

   names(kyphosis) 
[1] "Kyphosis" "Age"      "Number"   "Start"    
   formula(kyphosis) 
Kyphosis ~ Age + Number + Start