[R] Basic population dynamics

[Frostygoat]

Hello,

For insect mortality data I'm trying to get an R script that will take
the data from the raw form and convert it to Lx (% survival) for a
number of treatments.  The raw data has the number of days lived for
each individual for the respective treatment.  Thus, for example, when
R selects the data for a single treatment I end up with the following
vectors:

>day=seq(from=0,to=6)
>deaths=c(0,0,2,0,0,1,6)

where deaths is the number of deaths on a given day. Now I need to
create a new vector with the number alive for each day and this is
where I'm stuck... I've tried to work various for and while loops but
haven't had success.  The vector should be:

>Alive=c(9,9,7,7,7,6,0)

I realize it is a very basic problem that is easily accomplished in
one's head or on a spreadsheet but in the context of the size of the
data set I wish to have R do it for me. I would welcome any
suggestions please.

Best regards.