CODEWITHSUNDEEP
r
Janak
Janak

Reputation: 683

Get the indices of the last element of each run in vector

How to the get the index of last element of each run?

For example: Let us consider a vector 

x=c(1,2,3,4,4,4,5,6,6,7,8,9,9,9,9)

Want get the output vector

x1=1 2 3 6 7 9 10 11 15

Tried using:

rank(x)

It is not giving the desired result.

Upvotes: 1

Views: 69

Answers (2)

NinComPoop
NinComPoop

Reputation: 109

Using the which() function in R

    k<-as.vector(unique(x))
    x1<-vector()
    for(i in 1:length(k)){
        x1[i]=tail(which(x==k[i]),1)
    }

Upvotes: 1

talat
talat

Reputation: 70336

(Probably a dupe, but here you go..)

You can use the magic powers of ?rle combined with cumsum:

cumsum(rle(x)$lengths)
#[1]  1  2  3  6  7  9 10 11 15

The output of rle is:

rle(x)
#Run Length Encoding
#  lengths: int [1:9] 1 1 1 3 1 2 1 1 4
#  values : num [1:9] 1 2 3 4 5 6 7 8 9

Upvotes: 5

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