MATLAB: Slope of the linear(elastic) part of a stress-strain curve

stress-strain

So, I have a stress-strain curve. I need to find the slope of the linear part of the curve (a.k.a. Young's modulus) which is the region between the black lines.
I usually do this on Excel by drawing a trendline over this set of datapoints. How can this be done on Matlab ?
I would also need to do some corrections to the curves.
Related Question