Hi all, I have a curve that looks like this:

Let's name the points from left to right starting with 1.

I have to calculate the gradient of the line of best fit of the linear region. From the graph, it appears that the linear region is within points 2 and 4. However, the R-squared value of a line of best fit generated from points 1 to 3 is 0.99 whereas that from points 2 to 4 is only 0.92, as calculated by Microsoft Excel.

So should I choose points 1 to 3 or 2 to 4 as the linear region?