I have computer model output files that have >100,000 rows. Column A is the model time (days). Column B is a rate (meters/day). Each day is broken up into pieces, but not everyday is broken into the same number of pieces, i.e. day 1 consists of 22 rows while day 2 consists of 5 rows. What I need is the Average rate (meters/day) for each day, i.e. averaging the 22 rows for day 1 in Column B and averaging the 5 rows for day 2 in Column B, etc... I'm trying to write a formula that I can cut and paste because I have to do this for over 130 different model outputs. I attached an example of the data. Any help is much appreciated.