On Nov 21, 2011, at 11:42 AM, R. Michael Weylandt wrote:
I'd appreciate it if you'd keep on list for the archives. That said, I
think this function does what you were hoping for.
Michael
powerset <- function(n, items = NULL){
if(!is.null(items)) {
if(n != length(items)) warning("Resetting n in preference to
length(items)")
n = length(items)
}
smat <- do.call(expand.grid, rep(list(c(0,1)), n))
if(!is.null(items))
smat <- smat * matrix(items, ncol = n, nrow = 2^n, byrow = T)
smat
}
Michael's function is very nice (although the n= parameter seems
superfluous since any value other than the length of 'items' will get
discarded). However, your use case was not specified so I cannot know
if you wanted set notation or matrix class objects. Here's another
option in case you wanted set notation:
> require(sets)
Loading required package: sets
> as.set(c(2,3,4,5))
{2, 3, 4, 5}
> X <- as.set(c(2,3,4,5))
> set_power(X)
{{}, {2}, {3}, {4}, {5}, {2, 3}, {2, 4}, {2, 5}, {3, 4}, {3, 5}, {4, 5},
{2, 3, 4}, {2, 3, 5}, {2, 4, 5}, {3, 4, 5}, {2, 3, 4, 5}}
The set package offers an extensive list of set oriented functions.
--
David.
On Sat, Nov 19, 2011 at 8:49 PM, Gyanendra Pokharel
<gyanendra.pokha...@gmail.com> wrote:
Hi Michael,
I have trouble to find the subsets of a given set. For example x <-
c(2, 3,
4, 5), there will be 16 subsets of this set
in the matrix form
0 0 0 0
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
1 1 0 0
0 1 1 0
0 0 1 1
0 1 0 1
1 0 1 0
1 0 1 1
1 1 1 0
0 1 1 1
1 0 1 1
1 1 0 1
1 1 1 1
times transpose(x) , but how could I produce in R?
Thanks in advance
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David Winsemius, MD
West Hartford, CT
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and provide commented, minimal, self-contained, reproducible code.
