Drawing a straight line to a linear part of curve

Hello All, it would be very helpful if someone can help me out with drawing a straight line to the linear part of the curve in attached figure. I want to know the intercept value to the x-axis.

[dpb]

Nothing attached...

[KB]

Here is the figure...Thanks

Answer 1

[dpb]

Looks like piecewise regression to the rescue again...it has been the subject of some of my previous postings, one quite recent...

find-diverging-point-of-two-arrays

Having solved for the breakpoint, you'll also have the coefficients of the two line segments which can be readily used individually.