How to take the mean of each four adjacent position in a matrix?

So I have this matrix variable that I attached here. Its 1536 by 2048, and I want to reduce it to 768 by 1024 by taking the mean of each four adjacent positions with the omitnan opition as well so I can take out the useless NaNs there. I hope someone can help. Thanks

Answer 1

[Chuguang Pan]

A=randi(10,1536,2048); % test Matrix
M=zeros(768,1024); % result Matrix

for row=1:768
    for col=1:1024
        M(row,col)=mean(A(2*row-1:2*row,2*col-1:2*col),'all','omitnan');
    end
end