| Type: | Package |
| Title: | Efficient Iterator for Permutations and Combinations |
| Version: | 0.4.2 |
| Date: | 2020-01-08 |
| Author: | Randy Lai [aut, cre] |
| Maintainer: | Randy Lai <randy.cs.lai@gmail.com> |
| Description: | Iterator for generating permutations and combinations. They can be either drawn with or without replacement, or with distinct/ non-distinct items (multiset). The generated sequences are in lexicographical order (dictionary order). The algorithms to generate permutations and combinations are memory efficient. These iterative algorithms enable users to process all sequences without putting all results in the memory at the same time. The algorithms are written in C/C++ for faster performance. Note: 'iterpc' is no longer being maintained. Users are recommended to switch to 'arrangements'. |
| URL: | https://randy3k.github.io/iterpc |
| License: | GPL-2 |
| Depends: | R (≥ 3.0.0) |
| Imports: | iterators, gmp (≥ 0.5-12), arrangements (≥ 1.0.0) |
| Suggests: | foreach, testthat, knitr, rmarkdown |
| ByteCompile: | yes |
| RoxygenNote: | 6.1.1 |
| VignetteBuilder: | knitr |
| NeedsCompilation: | no |
| Packaged: | 2020-01-08 23:22:25 UTC; randy |
| Repository: | CRAN |
| Date/Publication: | 2020-01-10 12:30:02 UTC |
Efficient Iterator for Permutations and Combinations
Description
Efficient Iterator for Permutations and Combinations
Initialize a iterator for permutations or combinations
Usage
iterpc(n, r = NULL, labels = NULL, ordered = FALSE,
replace = FALSE)
Arguments
n |
the length of the input sequence or a vector of frequencies for a multiset. |
r |
the length of the output sequence. If missing, equals to |
labels |
if |
ordered |
|
replace |
with/without replacement. Default is |
Value
a permutation/combination iterator
Examples
#1) all combinations of drawing 2 items from {1, 2, 3}
I <- iterpc(5, 2)
getall(I)
#2) continuing 1), get combination by combination
I <- iterpc(5, 2)
getnext(I) # return 1,2
getnext(I) # return 1,3
getnext(I, 2) # return next 2 results
#3) 3) all permutations of {1, 2, 3} and use of labels
I <- iterpc(3, labels=c("a", "b", "c"), ordered=TRUE)
getall(I)
#4) permutations of multiset and
I <- iterpc(c(2, 1, 1), labels=c("a", "b", "c"), ordered=TRUE)
getall(I)
#5) combinations with replacement and the use of table as input
x <- c("a","a","b","c")
I <- iterpc(table(x), 3, replace=TRUE)
getall(I)
Get all permutations/combinations for a iterator
Description
Get all permutations/combinations for a iterator
Usage
getall(I)
Arguments
I |
a permutation/combination iterator |
Value
next permutation/combination sequence for the iterator I
Get the current element of a iterator
Description
Get the current element of a iterator
Usage
getcurrent(I)
Arguments
I |
a permutation/combination iterator |
Value
current element of a iterator
Get the length for a iterator
Description
Get the length for a iterator
Usage
getlength(I, bigz = FALSE)
Arguments
I |
a permutations/combinations iterator |
bigz |
use gmp's Big Interger |
Value
an integer
Get the next permutation(s)/combination(s) for a iterator
Description
Get the next permutation(s)/combination(s) for a iterator
Usage
getnext(I, d = 1, drop = TRUE)
Arguments
I |
a permutation/combination iterator |
d |
number of permutation(s)/combination(s) wanted, default to 1 |
drop |
if |
Value
next d permutation(s)/combination(s) sequence for the iterator I
Wrap iterpc objects by iterators::iter
Description
Wrap iterpc objects by iterators::iter
Usage
iter_wrapper(I, d = 1)
Arguments
I |
the iterpc object |
d |
number of permutation(s)/combination(s) wanted in each iteration, default to 1 |
Value
a iter object compatible with iterators package
Examples
library(iterators)
I <- iterpc(5, 2)
it <- iter_wrapper(I)
nextElem(it)
nextElem(it)
library(foreach)
I <- iterpc(5, 2)
it <- iter_wrapper(I)
foreach(x=it, .combine=c) %do% { sum(x) }
Calculate multinomial coefficient
Description
This function calculates the multinomial coefficient
\frac{(\sum n_j)!}{\prod n_j!}.
where n_j's are the number of multiplicities in the multiset.
Usage
multichoose(n, bigz = FALSE)
Arguments
n |
a vector of group sizes |
bigz |
use gmp's Big Interger |
Value
multinomial coefficient
Examples
# (3+1+1)!/ (3! 1! 1!) = 20
multichoose(c(3,1,1))
Calculate the number of r-combinations of a multiset
Description
Calculate the number of r-combinations of a multiset
Usage
nc_multiset(f, r, bigz = FALSE)
Arguments
f |
the frequencies of the mutliset |
r |
the number of object drawn from the multiset |
bigz |
use gmp's Big Interger |
Value
the number of combinations (Big Integer from gmp)
Examples
x <- c("a","a","b")
# possible combinations of size 2 are "aa" and "ab".
nc_multiset(table(x), 2) # <- 2
Calculate the number of r-permutations of a multiset
Description
Calculate the number of r-permutations of a multiset
Usage
np_multiset(f, r, bigz = FALSE)
Arguments
f |
the frequencies of the mutliset |
r |
the number of object drawn from the multiset |
bigz |
use gmp's Big Interger |
Value
the number of r-permutations (Big Integer from gmp)
Examples
x = c("a","a","b")
# possible permutations of size 2 are "aa", "ab" and "ba".
np_multiset(table(x), 2) # = 3