creating a reverse geometric sequence
Erik Iverson wrote:
Hello, Can anyone think of a non-iterative way to generate a decreasing geometric sequence in R? For example, for a hypothetical function dg, I would like:
> dg(20)
[1] 20 10 5 2 1
where I am using integer division by 2 to get each subsequent value in the
sequence.
There is of course:
dg <- function(x) {
res <- integer()
while(x >= 1) {
res <- c(res, x)
x <- x %/% 2
}
res
}
> dg(20)
[1] 20 10 5 2 1 This implementation of 'dg' uses an interative 'while' loop. I'm simply wondering if there is a way to vectorize this process?
Something like this should work, at least for integer bases: base <- 2 len <- ceiling(log(x, base)) floor(x/base^(seq_len(len)-1)) Duncan Murdoch