Problem by creating Sub Matrices

I have 5x5 matrix.I want to create 6 submatrices of order 3x3.Uploaded the pic please any one can do it.Or any other methods to do this operation.Thanks

Answer 1

[Stephen23]

The more that you set up before the loop, the neater and clearer the code will be:

mat = reshape(1:25,5,5).'; % input matrix, any size
%
blkR = 3; % output block rows
blkC = 3; % output block columns
stpR = 2; % step size rows
stpC = 1; % step size columns
%
inSz = size(mat);
vecR = blkR:stpR:inSz(1); % blocks' end rows
vecC = blkC:stpC:inSz(2); % blocks' end columns
%
numR = numel(vecR); % count blocks along rows 
numC = numel(vecC); % count blocks along columns
out = cell(numR,numC);
for kR = 1:numR
    for kC = 1:numC
        idxR = vecR(kR)+(1:blkR)-blkR; % row indices
        idxC = vecC(kC)+(1:blkC)-blkC; % column indices
        out{kR,kC} = mat(idxR,idxC); % use indices
    end
end

and checking the output:

>> out{:}
ans =
     1     2     3
     6     7     8
    11    12    13
ans =
    11    12    13
    16    17    18
    21    22    23
ans =
     2     3     4
     7     8     9
    12    13    14
ans =
    12    13    14
    17    18    19
    22    23    24
ans =
     3     4     5
     8     9    10
    13    14    15
ans =
    13    14    15
    18    19    20
    23    24    25
>>

[Haseeb Hassan]

Thanks for your answer, please can you put the comments for more understanding as i am new bie in matlab and programming.

Answer 2

[MSP]

clear all
a=magic(5)
shiftr=2
shiftc=1
k=1
rowsize=3
colsize=3
for i=1:shiftr:size(a,1)
        if i+rowsize-1>size(a,1)    %%check whether b matrix indices is within a If not then break-i loop 
            break
        end
    for j=1:shiftc:size(a,2)
       if (j+colsize-1)>size(a,2)
            break
       else 
        b(:,:,k)=a(i:i+rowsize-1,j:j+colsize-1)
        k=k+1;
       end       
    end
   j=1;    
end

This is the most basic format of doing it.Have a look and ask if u don't understand.

[Haseeb Hassan]

Thanks mate, the program working properly, but i am new to this plateform please help to understand me more clearly if you dont mind.I have problem to understand the logic of for loop. Please expalin more with clear information thanks