"index exceeds matrix dimension" error

I want to calculate perimeter of a triangle formed by three anchor node a,b and c, in wireless sensor network. following is my code, any one help please how this error can be solved

function perim = perimeter(AB,AC,BC)

     perim = AB+AC+BC;  % perimeter of virtual triangle ABC which is formed by anchor node A,B and C.  .
       if neighboring_anchor_n>=3
              gridmap=zeros(row_n,col_n);
              grid_covered_flag=zeros(row_n,col_n);
         for a=1:neighboring_anchor_n-2
                 for b=a+1:neighboring_anchor_n-1
                     for c=b+1:neighboring_anchor_n
                      neighboring_node_index=setdiff(find(neighbor_matrix(i,:)==1),neighboring_anchor_index([a b c]));

     perim =sqrt(transpose((neighboring_anchor_n(1,1)-neighboring_anchor_n(2,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(2,2)).^2)+sqrt(transpose((neighboring_anchor_n(1,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(3,2)).^2)+sqrt(transpose((neighboring_anchor_n(2,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(2,2)-neighboring_anchor_n(3,2)).^2);          

       end 
    end

Thank you for your help in advance.

[KSSV]

What input you tried? Which line shows error?

[Kelil Mohammed]

line 10 Sir.

[Bob Thompson]

For future reference it's a bit easier if you paste the line itself, rather than the number, as many people post incomplete code, so your error message might say 'line 10' but it's actually line 6 of the posted code. I assume that is not the case here because you have posted a function, but for future reference.

[James Tursa]

I don't see where neighboring_anchor or neighboring_anchor_index come from. What are they? What size are they? Is this a nested function?