Sequences

Hi,

I am trying to make a sequence and am  using a for loop for this. I want to
start off with an initial value ie S[0]=0 then use the loop to create other
values. This is what I have so far but I just keep getting error messages.

#To calculate the culmulative sums:

s<-rep(0,207)                                #as this is the length of the
vector I know I will have
s<-as.vector(s)
s[0]<-0
for (i in 1:length(lambs))                    # where lambs is a vector of
length 207 consisting of temperature 
                                                                    values


{
	s[i]<-s[i-1]-mean(lambs)
}

I continually get the error message: 

Error in s[i] <- s[i - 1] - mean(lambs) : replacement has length zero


When I merely use s[i]<-i-mean(lambs) it works so there is obviously
something wrong with the s[i-1] but i cant see what. All I want is for each
S[i] to be the previous value for S - the mean.