Finding similarity measure between 2 plots..?

sorry if my question sounds very amateurish..

Actually I have a set of plots in 2d form

Let X=(x1,x2...xn) be a 开发者_运维知识库set of similar plots obtained

Y=(y1,y2...yn) be a set of plots similar

Intuitively i can see that all plots of X 'look similar' But how do i find the similarity between scores between 2 plots and prove that they have a high similarity score..??

I am using the R language... Can somebody help..??Thanks

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It seems that you are thinking of the case in which both plots have a value at any given position. Maybe this method will work:

For each index i, calculate (xi-yi)^2. Sum over all i. Divide by n.

This just calculates the average difference between points in the plot, so 0 would be exactly the same, while larger values mean less similarity. Statistically, there's probably a more accurately method, but this is a good estimate for sure.