MATLAB: Substracting every row from each other

Question

I am trying to substract every other row using 2 loops, what is wrong with this code?

Here is the code,

% these are the coordinates I am using 
coor=[x' y' z'];
%number of  the rows is my atomnumber 
atomnum=size(x,2);
contactmapdistance=zeros;
for i=atomnum : 1
    for j= 1:atomnum
        contactmapdistance(i,3)=coor(i,:) - coor(j,:);
        i=i-1;
    end
    j=j+1;
end

Answer 1

coor - reshape(coor.',1,size(coor,2),[])