how to perform as.factor function : i'm having multiple Data.frame namely Accident,Vehicles and Casualties which are to be merged in a single data.frame as Accidents .how to find the factors of the combined data.frame that is how to find factors of Accidents? 



##  $ accident_severity           : char  "Serious" "Slight" "Slight" "Slight" ...
##  $ number_of_vehicles          : int  1 1 2 2 1 1 2 2 2 2 ...
##  $ number_of_casualties        : int  1 1 1 1 1 1 1 1 1 1 ...
##  $ date                        : char  "04/01/2005" "05/01/2005" "06/01/2005" "06/01/2005" ...
##  $ day_of_week                 : char  "Tuesday" "Wednesday" "Thursday" "Thursday" ...
##  $ time                        : char  "17:42" "17:36" "00:15" "00:15" ...