controller code for access to params in radio button column

I am new to Rails, and I thought I understood params, but I'm a little fuzzy on what goes into the controller to access a third value for a radio button. In my migration I defined the column as a string with a default value of nil. The column itself is actually a question(no question mark appears in the column though)with three choices in the radio button form: yes, no, and undecided. Everything works fine, but I don't know how to get undecided to display in the table instead of yes. I'm sure this is a common scenario, but I can't seem to get the controller stuff right, HELP! This is what I currently have in my controller:

def Undecided   #GET /achvrs/Radio_ButtonValues   radio_button_results = params[:undecided_id].split   ["Yes" "No" "Undecided"]   PUTS params[:id] end

Thanks in advance, --Stacey