? about sample

i am trying to use the
sample command and have one question about it:
i am getting the error

Error in sample(length(x), size, replace, prob) :
        insufficient positive probabilities

when i use something like:
sample (1:4, prob=c(0,0,1,0))[1]

i was expecting that to return a 3 every time
while this is not exactly what i am using it for, i need the capabilities to
deal with zeros (as the probability valuees that i will be using wil vary,
and sometimes will include zeros), and this seems like the zero's are the
problem...

currently i am assigning zero values in my initial probability vector to a
miniscule value(1E-4)

is there a more efficient way to deal with this, or another command that
does a similar thing to only select a single element, where as sample orders
the entire set according to the prob?