I am working with a dataset where each row is a record of a gas station fill up for a fleet of busses. One of the fields is the odometer reading. I would like to get the total mileage driven for the entire fleet for a month. So I need to find the sum total of the last odometer reading of each vehicle per month, and get the difference month over month. What is the best way to approach this?
Note: in my attached example I am working with max odometer readings, but I think it would be more accurate to say last odometer reading in the month (in case there was an entry error).