I wish to perform moving tiles bootstrap resampling on some gridded data
meteorological data. I've many years experience with S-Plus, but it has
no way to perform a moving-tiles bootstrap. Within R I've learned how to
use quadratresample() with the spatstats package and would be happy to
simply use empirical percentiles if generating the replicates were fast,
but it isn't. So, I'd like to employ bootstrap tilting to generate my
confidence intervals. On my machine (older Athlon, XP sp3, 4 GB) it took
about 48 h to generate 5000 moving tiles replicates. But, the boot
package contains boot.tilt and I should be able to do well enough with
the statistics I need (mean and RMS) to get by with several hundred
samples instead of several thousand.
I can certainly build a function that generates the statistic I want
from a moving-tiles replicate. My problem is that the resampling process
isn't as simple as boot.tilt() expects (I'm not simply resampling rows
of a data frame). But, the function that does what I need doesn't fit
into how boot.tilt() expects the resampling process to work. I can
generate a string of replicates easily enough -- how might I wrap such a
set of replicates into an object on which tilting could be performed
absent the internal generation of the replicates themselves?
Kim Elmore
--
Kim Elmore, Ph.D. (CCM, PP SEL/MEL/Glider, N5OP, 2nd Class
Radiotelegraph, GROL)
/"Human beings, who are almost unique in having the ability to learn
from the experience/
/of//others, are also remarkable for their apparent disinclination to do
so/."/-- Douglas Adams/
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