extracting particular row and column

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Tanmoyee Bhattacharya
评论： Tanmoyee Bhattacharya 2016-5-4
I have a matrix like this
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
5 6 7 8
5 6 7 8
5 6 7 8
5 6 7 8
9 10 11 12
9 10 11 12
9 10 11 12
9 10 11 12
like that so many rows.I want to extract every 4 row and 4 column continuously for whole row and save it in excel file.For a single row it works b=a(1:1:4),:);but for all row how can it possible.

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采纳的回答

Guillaume
Guillaume 2016-5-3
Do you mean?
b = a(1:4:end, :)
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Guillaume
Guillaume 2016-5-3
编辑：Guillaume 2016-5-3
I believe this is what you want:
assert(mod(size(a, 1), 4) == 0, 'number of rows is not a multiple of 4');
numcells = size(a, 1) / 4; %number of matrices generated
b = mat2cell(a, ones(1, numcells)*4, size(a, 2)); %split a into matrices
%save as excel file however you want, e.g.:
savepath = 'C:\wherever\you want\to save your files\');
for bidx = 1:numcells
xlswrite(fullfile(savepath, sprintf('%4d.xlsx', bidx)), b{bidx});
end

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更多回答（1 个）

Image Analyst
Image Analyst 2016-5-3
Guillaume's first answer gave you every 4th row extracted from the original, and all columns will be included. Perhaps when you say you "want to extract every 4 row and 4 column" you want this:
m4 = m(1:4:end, 1:4:end);
or
m4 = imresize(m, 0.25, 'nearest');
This will subsample the matrix by 4 in both the row and column direction.

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