Combinations generator (combinatorics) Generates all possible combinations of (n/k) k elements from n elements with no repetitions. Iterate or display combinations.
npm install combination_gen::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Javascript module to work with combinations.
Generate (n/k) combinations, iterate and work with them.
Available as a js file, and as a node.js npm package:
* node.js npm package -> master branch
* plain .js component -> no_npm branch
MIT License (MIT)
#### tags
combinations, javascript, basic combinatorics, set,
k-combinations,
this module can generate all the possible
combinations of a subset of number k distinct
elements, from a set of n elements, where the order
does not matter.
The combinations can be listed for examination, or can
be iterated over.
The total number of possible combination for n and k,
is given by:
/ n \ = n! for k <= n
\ k / k! (n-k)!
http://en.wikipedia.org/wiki/Combination
#### node.js package
To install with npm, as a node.js package:
With command line, navigate to the folder where will be installed and enter:
npm install combination_gen
Then In javascript, import with require:
var combination_gen = require('combination_gen')
#### plain javascript
To install as a plain javascript file:
In github select the no_npm branch, and download with the link there.
Include the combination_gen.js file in your project.
There are two ways to use this component:
To explore combinations (n/k)
Specify values for n and k, and explore the combinations.
To operate over combinations of items.
Specify the items in the set, and the size k of the subsets.
Operate over the combiantions.
Specify values for n and k
combination_gen.n = 6
combination_gen.k = 4
Draw to console a matrix of the combinations ( to console.log() )
combination_gen.draw_matrix()
This method will iterate for all the combinations, and output
them, well formated, to console.log
Will output this:
:: combinations matrix ::
In this matrix each row is a possible combination.
Each column is an element of the set of n elements.
An o means the element is included.
An - means the element is not included.
[ 0 1 2 3 4 5 ]
[ o o o o - - ] 1
[ o o o - o - ] 2
[ o o o - - o ] 3
[ o o - o o - ] 4
[ o o - o - o ] 5
[ o o - - o o ] 6
[ o - o o o - ] 7
[ o - o o - o ] 8
[ o - o - o o ] 9
[ o - - o o o ] 10
[ - o o o o - ] 11
[ - o o o - o ] 12
[ - o o - o o ] 13
[ - o - o o o ] 14
[ - - o o o o ] 15
Add items to the set
combination_gen.add( 'blue' )
combination_gen.add( 'orange' )
combination_gen.add( 'purple' )
Each item added will adjust the value of n appropiately.
Specify a value for k
combination_gen.k = 2
List all the combinations ( to console.log() )
combination_gen.list()
Will output this
:: combinations list ::
List all possible combinations
For the values of k and n.
[ blue orange ] 1
[ blue purple ] 2
[ orange purple ] 3
This method will iterate for all the combinations, and output
them, well formated, to console.log.
toString() will be called on each item.
Draw to console a matrix of the combinations ( to console.log() )
combination_gen.draw_matrix()
Other than displaying the combinations for exploring,
This module also allow to iterate and work over the
combinations.
Add items to the set
combination_gen.add( 'blue' )
combination_gen.add( 'orange' )
combination_gen.add( 'purple' )
Specify a value for k
combination_gen.k = 2
Build the set
combination_gen.build()
This will create the set, and set it to an initial value.
This method should be called after changing n,k or adding
items.
Methods draw_matrix and list call it before strating to
iterate.
Get the current combination as an array of items:
combination_gen.get_combination()
Will return an array:
[ 'blue', 'orange' ]
Get the current combination as an array of booleans:
combination_gen.set
will return:
[ true, true, false ]
where each value correspond to an item, and is true
if the item is included in the current combination,
or false if it is not.
Iterate to the next combination
combination_gen.next()
Will return true, if the iteration was successful,
or false if the current iteration is the last. So it can
be easily used in loops.
Return to the first combination with:
combination_gen.build()
Will recreate the set, and set it to the initial position,
Ready for iteration.
#### This section content is pending
combination_gen.n
combination_gen.k
combination_gen.set
combination_gen.add()
combination_gen.build()
combination_gen.next()
combination_gen.get_combination()
combination_gen.list()
combination_gen.draw_matrix()