clc
clear all
% special matrices
disp('Example 3 - Identity matrix?')
% check the diagonal elements for = 1
% check the non-diagonal elements for = 0
% INPUTS
a=[1 0 0; 0 1 0; 0 0 1];
disp('Input matrix')
disp(a)
% CODE
[m,n]=size(a);
if m~=n
    disp('  Error - Matrix is not square')
else
    sq_count=0;  % starting point for non-diagonal
    id_count=0;  % starting point for diagonal
    for i=1:1:m
        for j=1:1:n
            % check the diagonals
            if a(i,j)==1 & i==j
                id_count=id_count+1;
            end
            % check the non-diagonals
            if a(i,j)==0 & i~=j
                sq_count=sq_count+1;
            end
        end
    end
    if sq_count==n^2-n & id_count==n
        disp('This is an identity matrix')
    else
        disp('This is not an identity matrix')
    end
end