# output of fun is not a matrix the same size as the block in block proc

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Kasra Sadatsharifi on 16 Dec 2020
Commented: Ameer Hamza on 18 Dec 2020
Hello,
I am trying to divid my image into distinct block and perform a function on each one of them. The output of my function would be two column matrices of coordinates and with each iteration the number of coordinates will not be the same(different number of points with specific features in each block). What should I do to be able to stack the coordinates into a two column matrix at each iteration so at the end I have a bunch of XY coordinates?
Thank you

Ameer Hamza on 16 Dec 2020
Edited: Ameer Hamza on 16 Dec 2020
You can create a cell array for saving data in each iteration and then stack them together at the end
xy_cell = cell(1,N); % it assumes you have N blocks
for i = 1:N
% calculate x and y coordinates
xy_cell{i} = [x y];
end
xy = vertcat(xy_cell{:})
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Ameer Hamza on 18 Dec 2020
In that case, blockproc() is not an appropriate function for you. You either need to use for loops or something like this
img = rand(100); % example matrix
C = mat2cell(img, 20*ones(1,size(img,1)/20), 20*ones(1,size(img,2)/20)); % divide image in blocks of 20x20
C_processed = cellfun(@fun, C, 'uni', 0); % fun the function you want to call on each block. It should return an nx2 matrix
xy = vertcat(C_processed{:});