Delete all rows except last one with that index

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.

Answer 1

[Star Strider]

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.

[R2]

That works perfectly thank you very much!

[Star Strider]

As always, my pleasure!