how to get odd rows and columns,even rows and columns

%A = randi(255, [1 10]);
% A = imread('lena1.jpg');
   A1 = imread('lena1.jpg');
    A=A1(:,1);
A = reshape(uint8(A), [1 512*1]);
s = size(A);
[rows columns numberOfColorBands] = size(A);
col1 = 1;
col2 = floor(columns/2);
col3 = col2 + 1;
row1 = 1;
row2 = floor(rows/2);
row3 = row2 + 1;
% Now crop
upperLeft = imcrop(A, [col1 row1 col2 row2])
count = zeros(1,256);
for i =1:s(1)
    for j =1:s(2)
        count(uint8(A(i,j)+1)) = count(uint8(A(i,j)+1))+1;
    end
end
count = double(count) /(512*1);
sumofprob=sum((count))
plot(count)

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Answer 1

Birdman 2018-3-13

3
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https://ww2.mathworks.cn/matlabcentral/answers/387924-how-to-get-odd-rows-and-columns-even-rows-and-columns#answer_309782

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Consider you have number of rows and columns which is an even number,

Odd rows:

A1(1:2:end-1,:)

Even rows:

A1(2:2:end,:)

Odd columns:

A1(:,1:2:end-1)

Even columns:

A1(:,2:2:end)

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Jos (10584) 2018-3-14

By substracting one, you discard the last odd row (column) when the number of rows (columns) of the array is odd. When this number is even, it does not matter, so just to be flexible, do not subtract one :)