R 2.6.0 has Reduce;
myvec <- c(2, 8, 24, 26, 51, 57, 58, 78, 219)
Reduce(function(myvec, p) setdiff(myvec, findSubsets2(p)), myvec, myvec)
On 9/16/07, Adrian Dusa <[EMAIL PROTECTED]> wrote:
>
> Dear list,
>
> I have a vector of numbers, let's say:
>
> myvec <- c(2, 8, 24, 26, 51, 57, 58, 78, 219)
>
> My task is to reduce this vector to non-reducible numbers; small numbers can
> cross-out some of the larger ones, based on a function let's say called
> reduce()
>
> If I apply the function to the first element 2, my vector gets shorted to:
> > (myvec <- reduce(myvec[1]))
> [1] 2 24 51 57 58 78 219
>
> The next element that can further reduce the vector is the second (24) and a
> next iteration further reduces it and so on, until nothing can be reduced.
>
> The question is, what is the best programming technique to achieve this?
>
> My crude solution is:
> ####
> position <- 1 # start with the first position in the vector (smallest number)
> while(position < length(myvec)) {
> myvec <- reduce(myvec[position])
> position <- position + 1
> }
> ####
>
> Is there a better programming approach?
> Some vectors have lengths of millions, so this one takes a very long time.
>
> Thanks in advance,
> Adrian
>
>
>
> PS: below is a self-contained example:
> The initial vector corresponds to the following lines in a base 3 matrix:
> [,1] [,2] [,3] [,4] [,5]
> 2 0 0 0 0 2
> 8 0 0 0 2 2
> 24 0 0 2 2 0
> 26 0 0 2 2 2
> 51 0 1 2 2 0
> 57 0 2 0 1 0
> 58 0 2 0 1 1
> 78 0 2 2 2 0
> 219 2 2 0 1 0
>
> In the first iteration, the first element 2 eliminates 8 and 26 because both
> contain number 2 in the last position (first line being shorter).
> The element 24 eliminates 51 and 78, and so on.
>
> `findSubsets2` <-
> function(element) {
> require(QCA)
> base3row <- getRow(rep(3,5), element, zerobased=TRUE)
> increment <- function(x, y) {
> a <- x
> for (i in 1:2) {
> a <- as.vector(outer(y, a, "+"))
> x <- c(x, a)
> }
> return(x)
> }
> indices <- which(base3row == 0)
> mbase <- c(81, 27, 9, 3, 1)
> for (i in indices) {
> element <- increment(element, mbase[i])
> }
> return(element[-1])
> }
>
> position <- 1
> while(position < length(myvec)) {
> falsevector <- findSubsets2(myvec[position])
> myvec <- setdiff(myvec, falsevector)
> position <- position + 1
> }
>
>
>
>
> --
> Adrian Dusa
> Romanian Social Data Archive
> 1, Schitu Magureanu Bd
> 050025 Bucharest sector 5
> Romania
> Tel./Fax: +40 21 3126618 \
> +40 21 3120210 / int.101
>
> ______________________________________________
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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