Vectorizing loop over vector elements

Question

I find it hard to come up with a fast solution to the following problem:

I have a vector of observations, which indicates the time of observation of certain phenomena. <

Answer 1

I'll try to be the one to offer a pure R solution:

example <- c(0,0,0,1,0,1,1,0,0,0,-1,0,0,-1,-1,0,0,1,0,0);

cs = cumsum(example!=0);
mch = match(cs, cs);
desired.output = example[mch];

print(cbind(example,desired.output))

UPD: It may be faster to calculate mch above with

mch = findInterval(cs-1,cs)+1

UPD2: I like the answer by @Roland. It can be shortened to two lines:

NN = (example != 0);
desired.output = c(example[1], example[NN])[cumsum(NN) + 1L];