Finding Last Non-Zero Value For Each Row
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Derrick Vaughn
on 11 May 2021
Commented: Image Analyst
on 11 May 2021
I have a 50x50 matrix (let's call it data) and I'm trying to find the last non-zero value for each row of the matrix. So far looking through other questions, I've seen answers for finding the positions of the last non-zero values or for applying this idea to arrays, but nothing on producing the actual values for a matrix. Any help is appreciated, thanks!
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Accepted Answer
Image Analyst
on 11 May 2021
Try this:
% Sample data
m = randi([0, 1], 10, 10)
[rows, columns] = size(m)
% Create an array to keep track of the column of the last 1 in each row.
lastNonZeroColumn = zeros(rows, 1);
% Loop over rows, finding the last 1 in each row.
for row = 1 : rows
% Find the last 1 in this row, if any exist.
col = find(m(row, :), 1, 'last');
if ~isempty(col)
% At least one 1 exists. Log it's location.
lastNonZeroColumn(row) = col;
end
end
% Display results in command window:
lastNonZeroColumn
2 Comments
Image Analyst
on 11 May 2021
So just log that value also:
% Sample data
m = randi([0, 9], 10, 10)
[rows, columns] = size(m)
% Create an array to keep track of the column of the last 1 in each row.
lastNonZeroColumn = zeros(rows, 1);
dataValues = nan(rows, 1);
% Loop over rows, finding the last 1 in each row.
for row = 1 : rows
% Find the last 1 in this row, if any exist.
col = find(m(row, :), 1, 'last');
if ~isempty(col)
% At least one 1 exists. Log it's location.
lastNonZeroColumn(row) = col;
dataValues(row) = m(row, col);
end
end
% Display results in command window:
lastNonZeroColumn
dataValues
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