Linear Interpolation

I am a true beginner as root.
I would like to make a linear interpolation. Indeed, during my data analysis, I get the following graph:

It is true that the slope is not obvious, but it exists and that is why I would like corrected. I just want to pass a line and then calculate the slope of this line.

But I do not know how to begin. Could you help me please?

Best regard.


See the “Fit Panel” in: ROOT Primer -> ROOT Basics -> Interactive ROOT