[R] Creating dataframe of all possible variable combinations

[Hosack, Michael]

Hello,

I need to create a dataframe containing all possible combinations of three variables: SITE (101,102,103,104), WDAY (MON,TUE,WED,THR,FRI), and TOD (MORN, AFTN). There should be a total of 40 unique combinations in my dataframe. I used expand.grid() successfully(?) to create my dataframe, but then when I went to order it by SITE, the resultant dataframe only contained four rows, one for each site. There must be something about this function that I don't understand. Any advice would be appreciated. 

Thank you,

Mike