Vectorize a product calculation which depends on previous elements?

Question

I\'m trying to speed up/vectorize some calculations in a time series. Can I vectorize a calculation in a for loop which can depend on results from an earlier iteration? For

Answer 1

Sometimes you just need to think about it totally differently. What you're doing is creating a vector where every item is the same as the first if it's a 1 or 0 otherwise.

z <- c(1,1,0,0,0,0)
if (z[1] != 1) z[1] <- 0
z[2:length(z)] <- z[1]