How to fix " Index exceeds matrix dimension" error?

I want to implement APIT (Approximate-Point-In_Triangle) localization algorithm for wireless sensor networks and some errors generated.here is my code.

   function APIT(all_nodes) 
            load 'coordinates.mat';
            load 'neighbor.mat';

       %all_nodes = anchor_nodes+unknown_nodes; 
            disp('Longer time, wait patiently...');
            unknown_node_index = all_nodes.anchors_n+1:all_nodes.nodes_n;
            row_n=ceil(all_nodes.square_L); 
            col_n=row_n;
            centroid_x=repmat(([1:col_n]-0.5),row_n,1); 
            centroid_y=repmat(transpose([1:row_n]-0.5),1,col_n);
            for i=unknown_node_index   
               disp([num2str(i),':I am running, donot press it ...']);
                neighboring_anchor_index=find(neighbor_matrix(i,1:all_nodes.anchors_n)==1);
                neighboring_anchor_n=length(neighboring_anchor_index);
                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])); 
                            perimeter(sqrt((neighboring_anchor_n(1,1)-neighboring_anchor_n(2,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(2,2)).^2), sqrt((neighboring_anchor_n(1,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(3,2)).^2), sqrt((neighboring_anchor_n(2,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(2,2)-neighboring_anchor_n(3,2)).^2));   
                               if perimeter > rss
                                    Grid_in_triangle_abc=inpolygon(centroid_x,centroid_y,all_nodes.estimated(neighboring_anchor_index([a b c]),1),all_nodes.estimated(neighboring_anchor_index([a b c]),2));%Grid covered by triangles abc
                                    gridmap=gridmap+Grid_in_triangle_abc;                            
                                end
                                grid_covered_flag=grid_covered_flag|Grid_in_triangle_abc;
                            end
                        end
                   if any(any(grid_covered_flag))
                        weight_max=max(max(gridmap(grid_covered_flag)));            
                        weight_max_index=intersect(find(gridmap==weight_max),find(grid_covered_flag==1));
                        [weight_max_ind_row,weight_max_ind_col]=ind2sub(size(gridmap),weight_max_index);
                        all_nodes.estimated(i,:)=mean([weight_max_ind_col weight_max_ind_row;weight_max_ind_col weight_max_ind_row]*grid_length-0.5*grid_length);
                        all_nodes.anc_flag(i)=2;
                   end
                     end
                end
            end
        end
The errors generated as follows:

Index exceeds matrix dimensions.

Error in APIT (line 30)

perimeter(sqrt((neighboring_anchor_n(1,1)-neighboring_anchor_n(2,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(2,2)).^2),
                        sqrt((neighboring_anchor_n(1,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(1,2)-neighboring_anchor_n(3,2)).^2),
                        sqrt((neighboring_anchor_n(2,1)-neighboring_anchor_n(3,1)).^2+(neighboring_anchor_n(2,2)-neighboring_anchor_n(3,2)).^2));

My mat files, APIT and Perimter codes are attached

Answer 1

[Stephen23]

You define the variable neighboring_anchor_n on line 21, with this:

neighboring_anchor_n=length(neighboring_anchor_index);

length always returns a scalar. Then on line 30 you try to access lots of elements of neighboring_anchor_n that simply do not exist (because it is scalar):

...neighboring_anchor_n(1,1)-neighboring_anchor_n(2,1)...
...neighboring_anchor_n(1,2)-neighboring_anchor_n(2,2)...
...
...neighboring_anchor_n(2,2)-neighboring_anchor_n(3,2)...

[Kelil Mohammed]

Thank you Sir for your response. Would you explain what have to change in line 30 of my code to fix the error.

[Stephen23]

@Kelil Mohammed: I have no idea. You have not explained anything about your code nor written any code comments. It is not clear what you expect to happen by accessing non-existent elements of a scalar, so I have no idea what you are trying to do.

[Kelil Mohammed]

Thank you Sir for your response. I want to find perimeter of a virtual triangle formed by three anchor nodes say anchor node A,B and C. say if coordinates are A(xa,ya),B(xb,yb) and C(xc,yc) and this is what I tried on line 30. Sir if you get my idea modify line 30 and explain for me. Thanks.