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Mark the next line with the same value in R

I have the following matrix with the name test:

            High Thresh Sig
2007-02-27 19.01  11.88   1
2007-03-01 19.40  17.29   1
2007-03-02 18.63  17.29   1
2007-03-14 21.25  20.41   1
2007-06-25 17.24  16.70   1
2007-06-27 18.98  18.89   1

I would like to drop the row in 2007-03-02, because it has the same value in the Thresh column as on the previous day.

I tried this:

test_shorter <- subset(test, diff(Thresh) !=0)

but it indexes the first entry, while I want to discard the second entry.

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1 answer

The function is duplicatedgreat for such situations. For instance:

> test[!duplicated(test[,'Thresh']),]
            High Thresh Sig
2007-02-27 19.01  11.88   1
2007-03-01 19.40  17.29   1
2007-03-14 21.25  20.41   1
2007-06-25 17.24  16.70   1
2007-06-27 18.98  18.89   1

If you need the same results as you, you can use the argument fromLast=:

> test[!duplicated(test[,'Thresh'], fromLast=TRUE),]
            High Thresh Sig
2007-02-27 19.01  11.88   1
2007-03-02 18.63  17.29   1
2007-03-14 21.25  20.41   1
2007-06-25 17.24  16.70   1
2007-06-27 18.98  18.89   1
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