On Thu, Apr 14, 2011 at 06:44:53PM +1200, Worik R wrote:
> To improve the efficiency of a process I am writing I would like to cache
> results. So I would like a data structure like a hash table.
>
> So if I call Z <- f(Y) I can cache Z associated with Y: CACHE[Y] <- Z
>
> I am stumped. I expected to be able to use a list for this but I cannot
> figure how....
If y is an integer, factor or string you could try something along these
lines:
cache <- list()
y <- 12
cache[[as.character(y)]] <- sqrt(y)
y<-98
cache[[as.character(y)]] <- sqrt(y)
cache
$`12`
[1] 3.464102
$`98`
[1] 9.899495
Of course this can get you in trouble if y is a floating point
number because of the issues with "identity" of such numbers, as
discussed in ?all.equal and FAQ 7.31 "Why doesn't R think these
numbers are equal?".
cu
Philipp
--
Dr. Philipp Pagel
Lehrstuhl für Genomorientierte Bioinformatik
Technische Universität München
Wissenschaftszentrum Weihenstephan
Maximus-von-Imhof-Forum 3
85354 Freising, Germany
http://webclu.bio.wzw.tum.de/~pagel
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