The error is clear......your indices are either negative or zeros double. When you are indexing, the indices should be either logical class (0,1) or positive integers.
Example:
A = [1 5 pi 2*pi cosd(90)] ;
A(1) % No error
A(-1) % error, becuase index is negative
A(0) % error becuase index is zero
idx = A > 1 ; % logical
A(idx) % no error, as idx is logical.
Int he same whay, use debuggig and check why the indices are neagtive.
