> More generally, you can always write a loop. They aren't necesssrily
fast
> or elegant, but they're pretty general. For example, to calculate
the max
> of the previous 50 observations (or fewer near the start of a
vector), you
> could do
>
> x <- ... some vector ...
>
> result <- numeric(length(x))
> for (i in seq_along(x)) {
> result[i] <- max( x[ max(1, i-49):i ])
> }
>
> Duncan Murdoch
>
You should be able to do the same as that loop with one of the *apply
functions as well, which would be cleaner and faster (usually).
Something like (this isn't real code and won't work)
x<-lapply(function(i,j) max(foo[i:j]), seq(1,N-50),seq(50,N))
(where foo is your original vector of length N)
Carl
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