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How to obtain a position of last non-zero element



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30UTC (7:30pm US/Eastern)
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The Ask Question Wizard is Live!How to trim leading and trailing whitespace?How do I replace NA values with zeros in an R dataframe?data.table vs dplyr: can one do something well the other can't or does poorly?Calculate days since last event in REfficient way of taking the max date within groupsTurn off verbose messages when loading tidyverse using library() functionColumn name of last non-NA row per row; using tidyverse solution?Filtering data relative to first and last occurance of an eventdplyr approach to get the last row number with a positive valueA code to imput missing values with linear dependency



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18















I've got a binary variable representing if event happened or not:



event <- c(0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0)


I need to obtain a variable that would indicate the time when the last event happened. The expected output would be:



last_event <- c(0, 0, 0, 0, 5, 5, 5, 5, 5, 5, 5, 5, 13, 13, 13, 13)


How can I obtain that with base R, tidyverse or any other way?










share|improve this question




























    18















    I've got a binary variable representing if event happened or not:



    event <- c(0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0)


    I need to obtain a variable that would indicate the time when the last event happened. The expected output would be:



    last_event <- c(0, 0, 0, 0, 5, 5, 5, 5, 5, 5, 5, 5, 13, 13, 13, 13)


    How can I obtain that with base R, tidyverse or any other way?










    share|improve this question
























      18












      18








      18


      1






      I've got a binary variable representing if event happened or not:



      event <- c(0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0)


      I need to obtain a variable that would indicate the time when the last event happened. The expected output would be:



      last_event <- c(0, 0, 0, 0, 5, 5, 5, 5, 5, 5, 5, 5, 13, 13, 13, 13)


      How can I obtain that with base R, tidyverse or any other way?










      share|improve this question














      I've got a binary variable representing if event happened or not:



      event <- c(0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0)


      I need to obtain a variable that would indicate the time when the last event happened. The expected output would be:



      last_event <- c(0, 0, 0, 0, 5, 5, 5, 5, 5, 5, 5, 5, 13, 13, 13, 13)


      How can I obtain that with base R, tidyverse or any other way?







      r tidyverse base






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Apr 11 at 14:08









      jakesjakes

      481315




      481315






















          4 Answers
          4






          active

          oldest

          votes


















          18














          Taking advantage of the fact that you have a binary vector, the following gives your desired output:



          cummax(seq_along(event) * event)





          share|improve this answer


















          • 6





            Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

            – Konrad Rudolph
            Apr 11 at 14:27






          • 3





            or without multiplication cummax(ifelse(event, seq_along(event), 0))

            – jogo
            Apr 11 at 14:27











          • @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

            – Konrad Rudolph
            Apr 11 at 14:28


















          8














          Whenever you need to fill repetitions with a value, think run-length encoding.



          In this case, you can determine the run lengths and then repeat the indices of count == 0 an according number of times:



          lengths = rle(event == 0)$lengths
          nonzeros = which(event != 0)
          runs = c(0, rep(nonzeros, each = 2))
          result = rep(runs, lengths)


          Alternative, substitute the runs in the RLE and then inverse it:



          rle = rle(event == 0)
          nonzeros = which(event != 0)
          rle$values = c(0, rep(nonzeros, each = 2))
          result = inverse.rle(rle)





          share|improve this answer






























            1














            You can also do somthing like this-



            > zero.locf <- function(x) 
            v <- x!=0
            c(0, x[v])[cumsum(v)+1]


            > zero.locf(1:length(event)*event)

            [1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





            share|improve this answer






























              1














              Another option is to find the index where event == 1 and repeat it based on length.



              rep(c(0, which(event == 1)), tapply(event, cumsum(event == 1), length))
              #[1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





              share|improve this answer























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                4 Answers
                4






                active

                oldest

                votes








                4 Answers
                4






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes









                18














                Taking advantage of the fact that you have a binary vector, the following gives your desired output:



                cummax(seq_along(event) * event)





                share|improve this answer


















                • 6





                  Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                  – Konrad Rudolph
                  Apr 11 at 14:27






                • 3





                  or without multiplication cummax(ifelse(event, seq_along(event), 0))

                  – jogo
                  Apr 11 at 14:27











                • @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                  – Konrad Rudolph
                  Apr 11 at 14:28















                18














                Taking advantage of the fact that you have a binary vector, the following gives your desired output:



                cummax(seq_along(event) * event)





                share|improve this answer


















                • 6





                  Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                  – Konrad Rudolph
                  Apr 11 at 14:27






                • 3





                  or without multiplication cummax(ifelse(event, seq_along(event), 0))

                  – jogo
                  Apr 11 at 14:27











                • @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                  – Konrad Rudolph
                  Apr 11 at 14:28













                18












                18








                18







                Taking advantage of the fact that you have a binary vector, the following gives your desired output:



                cummax(seq_along(event) * event)





                share|improve this answer













                Taking advantage of the fact that you have a binary vector, the following gives your desired output:



                cummax(seq_along(event) * event)






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Apr 11 at 14:24









                mgiormentimgiormenti

                444211




                444211







                • 6





                  Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                  – Konrad Rudolph
                  Apr 11 at 14:27






                • 3





                  or without multiplication cummax(ifelse(event, seq_along(event), 0))

                  – jogo
                  Apr 11 at 14:27











                • @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                  – Konrad Rudolph
                  Apr 11 at 14:28












                • 6





                  Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                  – Konrad Rudolph
                  Apr 11 at 14:27






                • 3





                  or without multiplication cummax(ifelse(event, seq_along(event), 0))

                  – jogo
                  Apr 11 at 14:27











                • @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                  – Konrad Rudolph
                  Apr 11 at 14:28







                6




                6





                Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                – Konrad Rudolph
                Apr 11 at 14:27





                Yes! So much more elegant than my solution. I was thinking about cumulative sums but I didn’t think of multiplying the indices by the binary vector.

                – Konrad Rudolph
                Apr 11 at 14:27




                3




                3





                or without multiplication cummax(ifelse(event, seq_along(event), 0))

                – jogo
                Apr 11 at 14:27





                or without multiplication cummax(ifelse(event, seq_along(event), 0))

                – jogo
                Apr 11 at 14:27













                @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                – Konrad Rudolph
                Apr 11 at 14:28





                @jogo That solution makes sense if the type of event is logical. It does work even for a numeric vector due to R’s implicit conversions but … eh.

                – Konrad Rudolph
                Apr 11 at 14:28













                8














                Whenever you need to fill repetitions with a value, think run-length encoding.



                In this case, you can determine the run lengths and then repeat the indices of count == 0 an according number of times:



                lengths = rle(event == 0)$lengths
                nonzeros = which(event != 0)
                runs = c(0, rep(nonzeros, each = 2))
                result = rep(runs, lengths)


                Alternative, substitute the runs in the RLE and then inverse it:



                rle = rle(event == 0)
                nonzeros = which(event != 0)
                rle$values = c(0, rep(nonzeros, each = 2))
                result = inverse.rle(rle)





                share|improve this answer



























                  8














                  Whenever you need to fill repetitions with a value, think run-length encoding.



                  In this case, you can determine the run lengths and then repeat the indices of count == 0 an according number of times:



                  lengths = rle(event == 0)$lengths
                  nonzeros = which(event != 0)
                  runs = c(0, rep(nonzeros, each = 2))
                  result = rep(runs, lengths)


                  Alternative, substitute the runs in the RLE and then inverse it:



                  rle = rle(event == 0)
                  nonzeros = which(event != 0)
                  rle$values = c(0, rep(nonzeros, each = 2))
                  result = inverse.rle(rle)





                  share|improve this answer

























                    8












                    8








                    8







                    Whenever you need to fill repetitions with a value, think run-length encoding.



                    In this case, you can determine the run lengths and then repeat the indices of count == 0 an according number of times:



                    lengths = rle(event == 0)$lengths
                    nonzeros = which(event != 0)
                    runs = c(0, rep(nonzeros, each = 2))
                    result = rep(runs, lengths)


                    Alternative, substitute the runs in the RLE and then inverse it:



                    rle = rle(event == 0)
                    nonzeros = which(event != 0)
                    rle$values = c(0, rep(nonzeros, each = 2))
                    result = inverse.rle(rle)





                    share|improve this answer













                    Whenever you need to fill repetitions with a value, think run-length encoding.



                    In this case, you can determine the run lengths and then repeat the indices of count == 0 an according number of times:



                    lengths = rle(event == 0)$lengths
                    nonzeros = which(event != 0)
                    runs = c(0, rep(nonzeros, each = 2))
                    result = rep(runs, lengths)


                    Alternative, substitute the runs in the RLE and then inverse it:



                    rle = rle(event == 0)
                    nonzeros = which(event != 0)
                    rle$values = c(0, rep(nonzeros, each = 2))
                    result = inverse.rle(rle)






                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered Apr 11 at 14:23









                    Konrad RudolphKonrad Rudolph

                    404k1017951041




                    404k1017951041





















                        1














                        You can also do somthing like this-



                        > zero.locf <- function(x) 
                        v <- x!=0
                        c(0, x[v])[cumsum(v)+1]


                        > zero.locf(1:length(event)*event)

                        [1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                        share|improve this answer



























                          1














                          You can also do somthing like this-



                          > zero.locf <- function(x) 
                          v <- x!=0
                          c(0, x[v])[cumsum(v)+1]


                          > zero.locf(1:length(event)*event)

                          [1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                          share|improve this answer

























                            1












                            1








                            1







                            You can also do somthing like this-



                            > zero.locf <- function(x) 
                            v <- x!=0
                            c(0, x[v])[cumsum(v)+1]


                            > zero.locf(1:length(event)*event)

                            [1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                            share|improve this answer













                            You can also do somthing like this-



                            > zero.locf <- function(x) 
                            v <- x!=0
                            c(0, x[v])[cumsum(v)+1]


                            > zero.locf(1:length(event)*event)

                            [1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13






                            share|improve this answer












                            share|improve this answer



                            share|improve this answer










                            answered Apr 11 at 14:30









                            RushabhRushabh

                            1,332222




                            1,332222





















                                1














                                Another option is to find the index where event == 1 and repeat it based on length.



                                rep(c(0, which(event == 1)), tapply(event, cumsum(event == 1), length))
                                #[1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                                share|improve this answer



























                                  1














                                  Another option is to find the index where event == 1 and repeat it based on length.



                                  rep(c(0, which(event == 1)), tapply(event, cumsum(event == 1), length))
                                  #[1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                                  share|improve this answer

























                                    1












                                    1








                                    1







                                    Another option is to find the index where event == 1 and repeat it based on length.



                                    rep(c(0, which(event == 1)), tapply(event, cumsum(event == 1), length))
                                    #[1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13





                                    share|improve this answer













                                    Another option is to find the index where event == 1 and repeat it based on length.



                                    rep(c(0, which(event == 1)), tapply(event, cumsum(event == 1), length))
                                    #[1] 0 0 0 0 5 5 5 5 5 5 5 5 13 13 13 13






                                    share|improve this answer












                                    share|improve this answer



                                    share|improve this answer










                                    answered Apr 11 at 14:31









                                    Ronak ShahRonak Shah

                                    48.5k104369




                                    48.5k104369



























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