How to express the dynamics of a dataset with a single number?

Question

Mathematics

There are a number of products. And there is an indicator fixed for each of the goods on a specific day.
How can you compile the top products with the most "growing" indicator?
That is, how to express the direction of dynamics for each product in one figure, so that later they can be compared with each other?

Answer 1

Take for each product a set of points {day, indicator} for some of the last days. Plot a linear regression. The slope of the straight line (i.e. the coefficient in front of the day number) will be this indicator of dynamics.

Answer 2

Quantity of goods for the current day - quantity of goods for the previous day