[R] partial cumsum

[smu]

On Wed, Nov 11, 2009 at 08:53:50AM -0800, William Dunlap wrote:
> 
> Perhaps
>    > ave(x, rev(cumsum(rev(is.na(x)))), FUN=cumsum)
>     [1]  1  3  6 NA  5 11 18 26 35 45
> 

it takes some time to understand how it works, but it's perfect.

thank you,
 stefan