How to calculate mean and variance of object boundary?

Dear experts,

I'm trying to calculate mean and variance of object boundary as features in image.

I obtained boundary points from "bwboundaries". So I have a matrix n*2 that columns are x and y (the coordination of points on boundary).

My problem is how I can calculate mean and variance of boundary. I mean mean(A,1) and mean(A,2)is a mean point of boundary. Does this make sense?

Does anyone have a mathematics definition for mean and variance of boundary?