Lab 7 Practice Problems Engineering Computation, Dr S. Nasseri
Try these:
>> C= [ 3 2 0 3 4 4 2 1]
>> length(C) = 8
>> diff(A)
>> [-1 -2 3 1 0 -2 -1]
>> length(diff(C))
>> 7
Consider the following matrix A. Try the diff command for this matrix:
1 6
7 12
A= 3 0
14 9
6 1
, >>diff (A) = ?
6 6
-4 -12
11 9
-8 -8
Without typing “help diff”, try theses ones for the same matrix A and guess what each does (these
commands have applications in signal processing):
Af1= diff(A, 1)
6 6
-4 -12
11 9
-8 -8
First order difference along the first
dimension (Matlab does all the operations on
column by default, or you can say the operation
of row differences)
Af2 = diff(A, 2)
-10 -18
15 21
-19 -17
Second order difference along the first
dimension (Considers the diff(A,1)). This is
again the operation of row differences.
Af11 = diff(A,1,1)
6 6
-4 -12
11 9
-8 -8
First order difference along the first
dimension (the operation of row differences).
Af22= diff (A,1,2)
6 - 1 = 5
12-7 = 5
0 - 3 = -3
9-14 = -5
1- 6 = -5
First order difference along the second
dimension (the operation of column differences.)
Af12 = diff(A,2,1)
-10 -18
15 21
-19 -17
Second order difference along the first
dimension (the operation of row differences)
Af22 = diff (A,2,2)
Empty matrix: 5-by-0
Second order difference along the second
dimension (the operation of column
differences.). Since we have only one column, it
returns an empty matrix.
