Hi Andreas, assuming that the increment is always indicated by the same value (in your example 0), this could work:

df$a <- cumsum(seq_along(df$b) %in% which(df$b == 0)) df HTH, Ulrik On Sun, 6 Aug 2017 at 18:06 Bert Gunter <bgunter.4...@gmail.com> wrote: > Your specification is a bit unclear to me, so I'm not sure the below > is really what you want. For example, your example seems to imply that > a and b must be of the same length, but I do not see that your > description requires this. So the following may not be what you want > exactly, but one way to do this(there may be cleverer ones!) is to > make use of ?rep. Everything else is just fussy detail. (Your example > suggests that you should also learn about ?seq. Both of these should > be covered in any good R tutorial, which you should probably spend > time with if you haven't already). > > Anyway... > > ## WARNING: Not thoroughly tested! May (probably :-( ) contain bugs. > > f <- function(x,y,switch_val =0) > { > wh <- which(y == switch_val) > len <- length(wh) > len_x <- length(x) > if(!len) x > else if(wh[1] == 1){ > if(len ==1) return(rep(x[1],len_x)) > else { > wh <- wh[-1] > len <- len -1 > } > } > count <- c(wh[1]-1,diff(wh)) > if(wh[len] == len_x) count<- c(count,1) > else count <- c(count, len_x - wh[len] +1) > rep(x[seq_along(count)],times = count) > } > > > a <- c(1:5,1:8) > > b <- c(0:4,0:7) > > f(a,b) > [1] 1 1 1 1 1 2 2 2 2 2 2 2 2 > > > > 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 Sun, Aug 6, 2017 at 4:10 AM, Andras Farkas via R-help > <r-help@r-project.org> wrote: > > Dear All, > > > > wonder if you have thoughts on the following: > > > > let us say we have: > > > > > df<-data.frame(a=c(1,2,3,4,5,1,2,3,4,5,6,7,8),b=c(0,1,2,3,4,0,1,2,3,4,5,6,7)) > > > > > > I would like to rewrite values in column name "a" based on values in > column name "b", where based on a certain value of column "b" the next > value of column 'a' is prompted, in other words would like to have this as > a result: > > > > > df<-data.frame(a=c(1,1,1,1,1,2,2,2,2,2,2,2,2),b=c(0,1,2,3,4,0,1,2,3,4,5,6,7)) > > > > > > where at the value of 0 in column 'b' the number in column a changes > from 1 to 2. From the first zero value of column 'b' and until the next > zero in column 'b' the numbers would not change in 'a', ie: they are all 1 > in my example... then from 2 it would change to 3 again as 'b' will have > zero again in a row, and so on.. Would be grateful for a solution that > would allow me to set the values (from 'b') that determine how the values > get established in 'a' (ie: lets say instead of 0 I would want 3 being the > value where 1 changes to 2 in 'a') and that would be flexible to take into > account that the number of rows and the number of time 0 shows up in a row > in column 'b' may vary... > > > > much appreciate your thoughts.. > > > > Andras > > > > ______________________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.