Delete all rows except last one with that index
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I have two columns of data where I use the first as the ID and I want to delete all the rows with the same ID except for the last one with that ID. I cannot use unique as the corresponding value in the second column will always be different.
This is an over simplified example but should help explain what I mean:
2 12
4 6
5 24
5 39
5 15
5 18
11 18
14 5
14 6
23 5
Ideally I would hope to end up with the following as I always need to keep the last row with that ID:
2 12
4 6
5 18
11 18
14 6
23 5
Any help would be greatly appreciated.
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Accepted Answer
Star Strider
on 29 Jun 2017
Use the second output from the unique function on the flipud of your matrix:
M = [2 12
4 6
5 24
5 39
5 15
5 18
11 18
14 5
14 6
23 5];
Mf = flipud(M);
[~,ix] = unique(Mf(:,1));
Result = Mf(ix,:)
Result =
2 12
4 6
5 18
11 18
14 6
23 5
The second output of unique is the first instance of each unique element, so since your data are ordered, using flipud first returns the last element.
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