How to find the indices within blocks and sort the blocks thereafter?

Hi all,

Say I have the following matrix contains 15 elements:

       M =

           6     2     9
           7     2     3
           9     3    10
          10     9     4
           6     3     2

and the following coordinates which represent 4 blocks:

K>> block{:}
ans =
    -1    -1
     0    -1
     0     0
    -1     0
ans =
    -1     0
     0     0
     0     1
    -1     1
ans =
     0    -1
     1    -1
     1     0
     0     0
ans =
     0     0
     1     0
     1     1
     0     1

Now I'd like to separate the elements in M into 4 blocks using information in 'block' as the following picture:

So the result should be:

K>> mBlock{:}
ans =
     6     2
     7     2
     9     3
ans =
     2     9
     2     3
     3    10
ans =
     9     3
    10     9
     6     3
ans =
     3    10
     9     4
     3     2

How can I do it? Thanks a lot!

[Bob Thompson]

What is the logic behind the block creation? Will they always be the same (four quadrants)?

Answer 1

[Prajit T R]

Hi

Here's a code which will work for a size m x n matrix provided that m and n are odd values. To incorporate even values, you have to make some minor tweaks, that's all. You can divide a matrix into 4 quadrants as per your requirement using the following:

M =[6 2 9; 7 2 3; 9 3 10; 10 9 4; 6 3 2]; %The input matrix that needs to be divided
m=5; %number of rows
n=3; %number of coloumns
a=floor(m+1/2); %finding the midline of the rows
b=floor(n+1/2); %finding the midline of the coloumns
q1=M(1:a,1:b) %quadrant-1
q2=M(1:a,2:n) %quadrant-2
q3=M(a:m,1:b) %quadrant-3
q4=M(a:m,2:n) %quadrant-4

Hope this helps

Prajit