Remove rows in a matrix where there isn't a change larger than 3 in either column
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I have a 225x2 matrix where the first 200 rows or so (it varies by data set) does not change by more than 3 in either column. I need a function to delete all of the rows where there isn't a change greater than 3 and then condense the matrix.
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Image Analyst
on 6 Apr 2023
Do you mean a change between the first column and second column in each row?
Try this
changes = m(:, 2) - m(:, 1); % Change from col 1 to col 2.
rowsToDelete = changes > 3;
m = m(~rowsToDelete, :);
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Dyuman Joshi
on 6 Apr 2023
In the example you mentioned, both columns in the 2nd row don't change by more than 3 from the 1st row.
Now, do you want to remove the 2nd row, and compare the 3rd row to the first? Or do you want to compare the 3rd row to the 2nd one?
Image Analyst
on 6 Apr 2023
You forgot to give the output. Is the first row to be deleted too? Or just the second and third row?
m = [...
1000 520
1000 521
1001 519
800 250
324 104];
changes = diff(m, 1) % Change from one row to the next
rowsToDelete = [0; any(changes >= 0 & changes < 3, 2)]
m = m(~rowsToDelete, :)
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