How to find out point of change of sequence of ones and zeros?

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Lukas Poviser
Lukas Poviser 2021-7-27
评论： Lukas Poviser 2021-7-28
Hello,
I have this matrice:
1 NaN 3.28000000000000
1 NaN 3.32000000000000
1 NaN 3.36000000000000
1 NaN 3.40000000000000
0 0.0320040000000000 3.44000000000000
0 0.0697230000000000 3.48000000000000
0 0.124815600000000 3.52000000000000
0 0.158877000000000 3.56000000000000
and I would like to have another column where would be just the number where the first column changes from 1 to 0.
Result should be like this:
1 NaN 3.28000000000000
1 NaN 3.32000000000000
1 NaN 3.36000000000000
1 NaN 3.40000000000000 3.40000000000000
0 0.0320040000000000 3.44000000000000
0 0.0697230000000000 3.48000000000000
0 0.124815600000000 3.52000000000000
0 0.158877000000000 3.56000000000000

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采纳的回答

Jan
Jan 2021-7-27
编辑：Jan 2021-7-28
What do you expect in the other rows of the 4th column? All rows must have the same number of columns, according to the definition of a matrix. If zeros are fine:
index = find(A(:, 1) == 0, 1) - 1; % [EDITED, -1 appended]
if any(index)
A(index, 4) = A(index, 3);
end
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Jan
Jan 2021-7-28
Now you post another input, but do not mention, what you expect as output.
  • If you still want to use the first change from 1 to 0, use the code of my answer.
  • If you want to find all changes from 1 to 0:
index = strfind(A(:, 1).', [1, 0]);
B = A(index, 3);
% Alternative:
index = diff(A(:,1)) < 0;

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