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how to create a sequence to consecutive values

6 messages · Stefano Sofia, Jeff Newmiller, Bert Gunter

Stefano Sofia
# 
Dear R-list users,
this is a simple question, I have not been able to find an efficient solution.
Given a vector with only 0 or 1 values, I need to give a sequence to the consecutive values of 1:

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

I should get as result

(0,0,0,1,1,1,1,0,0,0,0,2,2,0,3,3,3,0,0)

I tried with ave, but no way to get it for me.

Thank you for your help
Stefano

         (oo)
--oOO--( )--OOo----------------
Stefano Sofia PhD
Civil Protection - Marche Region
Meteo Section
Snow Section
Via del Colle Ameno 5
60126 Torrette di Ancona, Ancona
Uff: 071 806 7743
E-mail: stefano.sofia at regione.marche.it
---Oo---------oO----------------

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Bert Gunter
# 
Using ?rle
< rep(v,z$lengths)
 [1] 0 0 0 1 1 1 1 0 0 0 0 2 2 0 3 3 3 0 0

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Aug 28, 2020 at 7:52 AM Stefano Sofia <
stefano.sofia at regione.marche.it> wrote:

            

      
      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Stefano Sofia
    

    

      
      #
    

  


  

      
Thank you!
Stefano

         (oo)
--oOO--( )--OOo----------------
Stefano Sofia PhD
Civil Protection - Marche Region
Meteo Section
Snow Section
Via del Colle Ameno 5
60126 Torrette di Ancona, Ancona
Uff: 071 806 7743
E-mail: stefano.sofia at regione.marche.it
---Oo---------oO----------------

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Jeff Newmiller
    

    

      
      #
    

  


  

      
cumsum is a bit faster...

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

f1 <- function(a) {
  z <- rle(a)
  v <- z$values
  v[v==1] <- seq_along(v[v==1]) ## or use cumsum
  rep(v,z$lengths)
}

f2 <- function(a) {
  v <- cumsum( c( a[1], 1==diff(a) ) )
  v[ 0==a ] <- 0
  v
}

f2(a)

library(microbenchmark)

a2 <- rep( c( 0,0, 1, 1, 1 )
         , 300 )

microbenchmark( res1 <- f1(a2)
              , res2 <- f2(a2)
              )
stopifnot( res1 == res2 )

        
On August 28, 2020 8:19:41 AM PDT, Stefano Sofia <stefano.sofia at regione.marche.it> wrote:

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Bert Gunter
    

    

      
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Actually, I prefer Jeff's use of diff() . Hadn't thought of that.

However, note that, unsurprisingly,  NA's mess up both: The rle() method
fails with an error and the diff() method gives the wrong answer.

Cheers,
Bert


On Fri, Aug 28, 2020 at 8:48 AM Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
wrote:

            

      
      
      
    

        

      
      
    

            
        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

  
  


  


      

    

    
2 days later

    

      
      

        


  

        

      Stefano Sofia
    

    

      
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Thank you both of you. I am studying these solutions.

Stefano

         (oo)
--oOO--( )--OOo----------------
Stefano Sofia PhD
Civil Protection - Marche Region
Meteo Section
Snow Section
Via del Colle Ameno 5
60126 Torrette di Ancona, Ancona
Uff: 071 806 7743
E-mail: stefano.sofia at regione.marche.it
---Oo---------oO----------------