Reporting a bug in build_epsilon_pos.m

[YumingN]

Hi there,

I run into problems sometimes in build_epsilon_pos.m at line 121 or line 125 due to the index of epsilon_pos, either because ind_ridge(1)-1 < 1, or because ind_ridge(2)+1 > ny causing dimension mismatching later. An index checking can be added to fix this.

Thanks for the code, I am learning a lot!
Best