Eigenvectors of ATA
Suppose (x,y) is on an edge.  What is ATA?
derive on board
•gradients along edge all point the same direction
•gradients away from edge have small magnitude
•     is an eigenvector with eigenvalue
•What’s the other eigenvector of ATA?
–let N be perpendicular to
–
–
–N is the second eigenvector with eigenvalue 0
The eigenvectors of ATA relate to edge direction and magnitude
Suppose M = vv^T .  What are the eigenvectors and eigenvalues?  Start by considering Mv