if i have two matrix how can make them same size by add zero column or row ?

if i have this matrix

 M = [15    13    11    11     7     7     8     9    11    13    15     8     8     6     3     0     3]
 X = [15    13    11    12     7     5     4     7     8     8    11     9    14    11    13 ]

i want to make X the same size of M and after that subtract them like that

 X_after = [15    13    11    12     7     5     4     7     8     8    11     9    14    11    13     0     0]

then abs(M - X_after) the final solution will be

 Final = [  0     0     0     1      0     2     4     2     3     5     4     1     6     5    10     0     3]

Answer 1

[dpb]

doc size
doc zeros

Read "Getting Started" section of documentation and work thru the tuorials on basic Matlab syntax and matrix/array operations.

Answer 2

[Stephen23]

M = [15,13,11,11,7,7,8,9,11,13,15,8,8,6,3,0,3];
X = [15,13,11,12,7,5,4,7,8,8,11,9,14,11,13];

tmp = zeros(2,max(numel(M),numel(X)));
tmp(1,1:numel(M)) = M;
tmp(2,1:numel(X)) = X;
out = abs(diff(tmp,1,1))

creates:

 out =
    0    0    0    1    0    2    4    2    3    5    4    1    6    5   10    0    3

And please do the introductory tutorials:

http://www.mathworks.com/help/matlab/getting-started-with-matlab.html