Offer your thoughts or opinion on the input financial query or topic using your financial background.

Shared groceries expenses between roommates to be divided as per specific consumption ratio and attendance
Bren's comment is right on the mark.  The typical solution is to divide all bills by 5, and for special items, the person buying it just marks his name that it's not community food.  Your attempt at a granularity level this detailed is admirable, but produces false results. What happens when I claim to be a zero percent milk drinker but when someone gives me cookies, I have a glass of milk?  The effort to get true accuracy will cost far more in time spent than the results are worth.