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How to replace arrays containing consecutive repeated numbers by zero?

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maruljay
maruljay 2020년 8월 24일
댓글: Adam Danz 2020년 8월 25일
I have a nested cell array that consists of vectors as shown in Fig. below:
I want to go through each cell array and check it if contains atleast 50% of consecutive repetated numbers. If the cell array contains such numbers, then I want to fill the entire cell array with zeros.
See example below. In this case all the elements of cell array contains consecutive repeated numbers. I want to replace the entire cell array with zeros.
Note: The reason why I mentioned 50% is that, there were many cell arrays where the first 36,000 or so elements were normal but the other half (36,000) contained consecutive repeated numbers.

채택된 답변

Adam Danz
Adam Danz 2020년 8월 24일
편집: Adam Danz 2020년 8월 24일
For some reason I'm drawn to detecting / counting consecutive numbers. I must have answered more than 5 questions similar to this one and every time I come up with a different convoluted solution that is usually way too difficult to read without dissecting it. This one's no exception. Let's see if it works with your data.
% Demo data
out = {[5;5;5;1;2;3];[1;2;2;2;5;5;5];[1;5;5;5;1];[0;1;1;0;1;1]};
% out{1} = out{2} = out3{3} = out{4} =
% 5 1 1 0
% 5 2 5 1
% 5 2 5 1
% 1 2 5 0
% 2 5 1 1
% 3 5
% 5
% Compute the length of the largest consecutive segment divided by
% the length of the full vector.
p = cellfun(@(v)max(accumarray(cumsum(diff(v([2,1:end]))~=0)+1,1))/numel(v), out);
% p =
% 0.5
% 0.42857
% 0.6
% 0.33333
% Replace entire vectors in "out" that contain a segment of consecutive values
% equal to or longer than 50% of the length of the vector, with zeros.
out(p>=0.5) = cellfun(@(v){zeros(size(v))},out(p>=0.5))
% out{1} = out{2} = out3{3} = out{4} =
% 0 1 0 0
% 0 2 0 1
% 0 2 0 1
% 0 2 0 0
% 0 5 0 1
% 0 5
% 5
The much-easier-to-read, unpacked, loop version of the cellfun() would look like
p = nan(size(out));
for i = 1:numel(out)
diffOut = diff(out{i}([2,1:end])); % 0s indicate a consecutive value.
nonConsecCount = cumsum(diffOut~=0); % Group consec. vals. with 0s and non-consec-vals with cumulative integers
consecCount = accumarray(nonConsecCount+1, 1); % The number of consec values for each segment
p(i) = max(consecCount)/numel(out{i}); % largest number of consec. / length of vector
end
  댓글 수: 2
maruljay
maruljay 2020년 8월 25일
편집: maruljay 2020년 8월 25일
Thank you so much. It worked like a charm. You just saved me tonnes of hours of work.
Your code explanation is crystal clear.
Adam Danz
Adam Danz 2020년 8월 25일
Glad it worked, thanks for letting us know!

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추가 답변 (1개)

Image Analyst
Image Analyst 2020년 8월 24일
Use a for loop and diff(). If you can't figure it out, attach a small chunk of your cell array in a .mat file.
  댓글 수: 1
maruljay
maruljay 2020년 8월 25일
Thanks for the insight. I have accepted the answer given by Adam Danz. It worked.

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