I have a dataset which has profile of wheel such that there are X coordinates and Y values, i.e. a set of (Xi, Yi) values (total about 1400 pairs of X and Y). These coordinates are measured different point of time (say one on January 1st, 2016 and other on Jan 31st, 2016). During this period there would have been some wear and tear on the surface and hence new set of observations (Xj, Yj) that is taken on Jan 31st, would see a graph below the above.
I want to calculate the difference between areas of two plots.
One approach I had in my mind to do through Riemann Sum, not sure if what I thought is correct approach.
Could someone please suggest me some ways of calculating this?