[racket] Plot, fit

I can't figure out how to use the function called fit, provided by the plot collection.

(fit f guess-list data) → fit-result?
  f : (real? ... . -> . real?)
  guess-list : (list/c (list symbol? real?))
  data : (or/c (list-of (vector/c real? real? real?))
         (list-of (vector/c real? real? real? real?)))

Are the first arguments to f the independent variables?
Are the symbols in the guess-list the names of the independent variables as defined in f?
How is the data arranged in each list-of vectors? 

rac