I'm searching what are the keywords or the good links to expand my researches.
I would like to get the equation ( for programming purposes ) of more or less this curve: https://i.stack.imgur.com/uv8rQ.png
Where the key values are: 1 for the "crossing point" in Y axis "before it goes infinite" 300 for the "crossing point" in X axis "before it goes infinite"
I would like to be able to manage the "curve amplitude"
Thanks in advance for any help
You're going to need a curve-fitting procedure and this is best done by computer.
EXCEL has simple best-fit graphing functions that would suffice for most purposes-what you'll need are points on the curve as the x and y coordinates.
In other words, the simple picture of the curve ain't gonna be good enough, you'll need actual coordinates. And I think this is true for any simple program you use,online or otherwise.
Another useful program for finding the best fitting equation can be found here:
https://www.easycalculation.com/statistics/trend-line.php
My advice to you is go back to the original plotting program and improve the "fineness" of the x and y grid coordinates. For example, instead of having the x axis in units of 100, make it in units of 10. You should be able to get coordinates then and use them to get the best fit equation.