calculate the averages of non-squared matrix blocks

Hi,

I have a non-squared matrix with a dimension of and I would like to calculate the averages of each block so I can get a average vector. A schematic explanation is shown below:

The matrix and the attempt I have is the following:

close all;
clear all;
%define the 12x4 matrix
A = [1 0 2 0;
    0 1 3 0 ;
    1 1 0 0 ;
    0 2 3 1 ;
    3 2 3 0 ;
    0 1 1 2 ;
    3 1 0 2 ;
    0 0 1 0 ;
    2 1 3 1 ;
    3 2 0 0 ;
    0 0 2 0 ;
    1 3 0 2];
%calculate the average of A for each 4x4 block
Points = 4;
for irow = 1:Points:size(A,1)
    for icol = 1:size(A,2)
        block_sum = 0;
        block_sum = block_sum + A(irow, icol);
    end
end
block_avg                   = block_sum / Points;
block_row                   = ceil(irow / Points);
block_col                   = ceil(icol / Points);
ave_A(block_row, block_col) = block_avg;

Any help would be appreciated. Thanks.

Answer 1

[Image Analyst]

Here is one way (there are others):

% Define the 12x4 matrix
A = [1 0 2 0;
    0 1 3 0 ;
    1 1 0 0 ;
    0 2 3 1 ;
    3 2 3 0 ;
    0 1 1 2 ;
    3 1 0 2 ;
    0 0 1 0 ;
    2 1 3 1 ;
    3 2 0 0 ;
    0 0 2 0 ;
    1 3 0 2];
%calculate the average of A for each 4x4 block
Points = 4;
index = 1;
for iRow = 1:Points:size(A,1)
    ave_A(index) = mean(A(iRow:iRow+Points-1, :), 'all');
    index = index + 1;
end
ave_A % Display in command window.

ave_A = 1×3

0.9375 1.1875 1.2500

Answer 2

[Dyuman Joshi]

A = [1 0 2 0;
    0 1 3 0 ;
    1 1 0 0 ;
    0 2 3 1 ;
    3 2 3 0 ;
    0 1 1 2 ;
    3 1 0 2 ;
    0 0 1 0 ;
    2 1 3 1 ;
    3 2 0 0 ;
    0 0 2 0 ;
    1 3 0 2];

%nxn block
n=4;

%Use conv2 to get mean of every nxn block of input array
B = conv2(A,ones(n),'valid')/n^2;

%Select every nth element
out = B(1:n:end)

ans = 3×1

0.9375 1.1875 1.2500