user2212372 user2212372 - 1 month ago 15
R Question

Remove all duplicates except last instance

So I have a dataset in R with the following layout as an example:

ID Date Tally
1 2/1/2011 1
2 2/1/2011 2
3 2/1/2011 3
1 2/1/2011 4
2 2/1/2011 5
1 2/1/2011 6
3 2/1/2011 7
4 2/1/2011 8
2 2/1/2011 9


I want to remove all instances except the LAST instance of the post id. Right now everything I can find online, and functions I am using is removing everything except the FIRST instance.

So my new data frame would look like:

ID Date Tally
1 2/1/2011 6
3 2/1/2011 7
4 2/1/2011 8
2 2/1/2011 9


How do I do this? Right now I am only able to keep the first instance. I want it to do the opposite? Any help?

Bear with me I am new to R :)

Answer

Use !rev(duplicated(rev(ID))) to filter out all but the last unique occurrences.

To get the dataset filtered, use dataset[!rev(duplicated(rev(dataset$ID))),]

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