This should be a very common mathematical need, but I'm having trouble finding a solution.
I have an MS-SQL database with a 1:M relationship between people and donations (relevant columns would be date, DI#, total). Obviously any given person can have any number of donations- typically less than 20 or 25. I need to determine whether any given person is trending up, down or basically staying the same in giving. I don't mind if they gave less in the middle, I'm looking for overall trend or trajectory.
Ideally I would like to be able to compare trends, so someone who is substantially increasing their giving has a higher score than someone who is slowly creeping up, but I can live with just an increasing, stable or decreasing return value.
Due to where in my code this sits, I am hoping to be able to do it without iteration. I do have a table already containing mean/average, first, last, largest, and count of donations, and can add more summaries if need be.
Is there a way I can compare various summaries to determine a trend, for example, a formula like if mean > median and largest-average>median, then it is increasing? I haven't found anything yet.
Thank you in advance.