I have some data that fits closely to an exponential curve on the left hand side and then flattens out on the right hand side. For the upper portion of the the curve, the data should fit closely to a straight line. I am trying to find a way to quantitatively work out exactly which part of my curve is 'most straight'.
I have tried qualitatively choosing the 'straightest' part of the data, which gives a good approximation, however I would like to do it quantitatively. I have also tried playing around in CFTOOL with to no avail.
See screenshot of data