[R] How to?
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Fri Aug 25 09:52:43 CEST 2000
On Fri, 25 Aug 2000, Martin Maechler wrote:
> >>>>> "Yves" == Yves Gauvreau <cyg at sympatico.ca> writes:
> Yves> In fact what I'd like to know is what is the most efficient R way
> Yves> to do thing like a moving average on a vector. Something generic
> Yves> enough that one could use practically any function on a constant
> Yves> width window of the vector?
> filter() from package ts ?
That's linear functions only. But I'm afraid that there is no
generic fast way to do this for arbitrary functions, which is why special
cases like filter() exists. The best I can think of is along the lines of
mywinfun <- function(x, width, FUN, ...)
n <- length(x) - width
z <- substr(x, 1:n, (1:n)+width)
sapply(z, FUN, ...)
which should beat the use of apply.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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