clear; clc;

a = [1,1,1,1]; % a   [1,1,1,1]

% returns the mean of elements of matrix 'a'. b 1
b = mean(a);

% create an identity matrix 4x4. c 4x4 double
c = eye(4,4);

% return a row vector where each element represents the mean of elements of
% the each column of matrix c.  d [0.250,0.250,0.250,0.250]
d = mean(c);

% return column vector where each element represents the mean of elements
% of the each row of matrix c. e [0.25;0.25;0.25;0.25]
e = mean(c,2);