[R] Creating Vectors

[Alexander Nervedi]

Hi all.

I have a factor variable distributed over time. I am looking for an elegant 
way to code duration of a state. Suppose,

>rainfall.shocks <- factor(sample(c(1,2,3), size = 15, replace = TRUE, prob 
>= unit.p),
+                  label = c("Drought", "Normal", "High"))
>
>rainfall.shocks
[1] Normal  High    High    Drought Normal  Normal  High    Normal  Drought
[10] Normal  Drought Normal  Normal  Normal  Normal


So capture the duration of say drought, I'd need a variable that is able to 
keep track of rainfall.shocks as well as its past values. I was wondering if 
there is any obvious way to do this. the Drought variable in this case would 
have values

0 0 0 1 0 0 0 0 1 0 1 0 0 0 0

many thanks for the suggestions you are likely to make.

Alexander Nervedi