Math - 1 month ago 9

R 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)`

`cumsum(x)`

[1] 1 2 3 4 5 5 6 6 6 6 7 8

Answer

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
```