Cumulative sum for positive numbers only [duplicate]

Question

I have this vector :

x = c(1,1,1,1,1,0,1,0,0,0,1,1) 

And I want to do a cumulative sum for the positive numbers only. I should have the following vector in return:

xc = (1,2,3,4,5,0,1,0,0,0,1,2) 

How could I do it?

I've tried : cumsum(x) but that do the cumulative sum for all values and gives :

cumsum(x) [1] 1 2 3 4 5 5 6 6 6 6 7 8 

Answer 1

One option is

x1 <- inverse.rle(within.list(rle(x), values[!!values] <-                    (cumsum(values))[!!values])) x[x1!=0] <- ave(x[x1!=0], x1[x1!=0], FUN=seq_along) x #[1] 1 2 3 4 5 0 1 0 0 0 1 2 

Or a one-line code would be

 x[x>0] <-  with(rle(x), sequence(lengths[!!values]))  x  #[1] 1 2 3 4 5 0 1 0 0 0 1 2 

Answer 2

Here's a possible solution using data.table v >= 1.9.5 and its new rleid funciton

library(data.table) as.data.table(x)[, cumsum(x), rleid(x)]$V1 ## [1] 1 2 3 4 5 0 1 0 0 0 1 2