markov alternatives and similar shards
Based on the "Algorithms and Data structures" category.
Alternatively, view markov alternatives based on common mentions on social networks and blogs.

crystalline
A collection of containers & algorithms for the Crystal programming language 
graphlb
graphlb is a crystal library which contains all the graph DataStructures and Algorithms implemented in crystallang. 
text
A collection of phonetic algorithms for Crystal. Including; PorterStemmer, Soundex, Metaphone, Double Metaphone & White Similarity 
crystallinkedlist
Simple linked list implementation in Crystal 
kd_tree
Crystal implementation of "KDimensional Tree" and "NNearest Neighbors" 
haversine
Crystal implementation of the Haversine formula to calculate distances between two points given their latitudes and longitudes 
edits.cr
Edit distance algorithms inc. Jaro, DamerauLevenshtein, and Optimal Alignment 
delimiter_tree
A crystallang tree structure that is built using a delimiter. 
murmur3
Crystal implementation of Murmur3 hash algorithm used by Cassandra 
ternary_search_tree
A Crystal implementation of a Ternary Search Tree 
splay_tree_map
This is a Crystal implementation of a Splay Tree; which is a type of binary search tree that is semibalanced and that tends to selfoptimize so that the most accessed items are the fastest to retrieve.
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README
⛓ Markov
A Crystal library for building Markov Chains and running Markov Processes.
What is a Markov Chain?
A Markov Chain is essentially a mechanism for guessing probable future events based on a sample of past events. For a great explanation, watch this Khan Academy video.
Visit the API Documentation for a more indepth look at the library's functionality.
Installation
Add this to your application's shard.yml
:
dependencies:
markov:
github: mccallofthewild/markov
In your terminal, install Crystal dependencies with:
$ shards install
or
$ crystal deps
Usage
Begin by requiring the Markov
module:
require "markov"
Basic  Hello Markov
A classic Markov text generator. This example will work well for small (arraysized) data sets.
NOTE: Markov::Chain
is a generic type which contains, receives and generates elements of LinkType
.
We'll start with the sample text:
example_string = "how much wood would a woodchuck chuck if a woodchuck could chuck wood"
There are several Markov::Chain
constructors to choose from. The simplest one takes in a LinkType
array of elements as sample
and a seed
of LinkType
. seed
is the element in sample
you want to start the chain with. If not provided, a random element will be chosen.
example_arr = example_string.split(" ") #=> ["how","much","wood","would","a","woodchuck","chuck","if","a","woodchuck","could","chuck","wood"]
seed = example_arr[0] #=> "how"
example_chain = Markov::Chain(String).new sample: example_arr, seed: seed
Finally, we'll generate a probable sequence of elements with the Markov::Chain#generate
method:
puts example_chain.generate(10)
Output:
["much", "wood", "would", "a", "woodchuck", "could", "chuck", "if", "a", "woodchuck"]
That's it!
If we wanted to get the elements one at a time, we could use the Markov::Chain#next
method instead:
puts example_chain.next #=> "much"
puts example_chain.next #=> "wood"
puts example_chain.next #=> "would"
Advanced
This implementation was built for larger data sets, with asynchronous input in mind.
In this example, we will create a Markov::Chain
which can generate realistic movie titles.
To begin, we instantiate a Markov::TransitionTable
. A TransitionTable
is a mechanism for training and implementing Markov processes.
example_table = Markov::TransitionTable(String).new
Markov::TransitionTable#add
Now we'll add a movie title using the Markov::TransitionTable#add
method:
movie_one = %w(the great gatsby) # shortcut syntax for ["the","great","gatsby"]
movie_one.each do word
example_table.add(word)
end
Markov::TransitionTable#add
adds elements one at a time. At a deeper level, it's adding each new word to the previous word's Transition Matrix (Markov::TransitionMatrix
).
Markov::TransitionTable#fill
For syntactic sugar, if we have an array of elements, we can avoid looping through and #add
ing them by using the Markov::TransitionTable#fill
method instead:
movie_one = %w(the great gatsby) # shortcut syntax for ["the","great","gatsby"]
example_table.fill table_with: movie_one
Markov::TransitionTable#reset
A problem arises at this point:
movie_two = %w(great expectations)
example_table.fill table_with: movie_two
The above code sequentially adds each word to the TransitionTable
. But The Great Gatsby and Great Expectations are two separate movie titles; the "Great" at the beginning of Great Expectations is not a probable transition from the "Gatsby" at the end of The Great Gatsby.
To solve this, use Markov::TransitionTable#reset
. #reset
clears the TransitionTable
's last added key, allowing us to separate titles like so:
movie_one = %w(the great gatsby)
example_table.fill table_with: movie_one
example_table.reset
movie_two = %w(great expectations)
example_table.fill table_with: movie_two
example_table.reset
movie_three = %w(the great escape)
example_table.fill table_with: movie_three
Implementing the TransitionTable
with a Markov::Chain
Finally, we can put the TransitionTable
to use by passing it to a Markov::Chain
constructor as transition_table
:
example_chain = Markov::Chain(String).new transition_table: example_table, seed: "great"
Handling Dead Ends
With small and/or unique data sets, Markov chains are fallible to reaching dead ends. That is, they can often reach a point where there is nothing to transition to.
When this happens in the Markov
module, Markov::Exceptions::EmptyTransitionMatrixException
is raised.
For example:
dead_end_array = %w(some say the world will end in fire)
dead_end_chain = Markov::Chain(String).new sample: dead_end_array, seed: "fire"
# nothing comes after "fire", so the chain is at a dead end.
dead_end_chain.next # raises `EmptyTransitionMatrixException`
To prevent this, use the Markov::Chain#on_dead_end
exception handler.
This method takes in a callback block with arguments of: the Markov::Chain
's @transition_table
, the Markov::Chain
instance, and the EmptyTransitionMatrixException
raised.
The block's return value of LinkType
fills in as the next item in the chain.
dead_end_array = %w(some say the world will end in fire)
dead_end_chain = Markov::Chain(String).new sample: dead_end_array, seed: "fire"
dead_end_chain.on_dead_end do transition_table, chain, exception
"some"
end
dead_end_chain.next #=> "some"
dead_end_chain.next #=> "say"
dead_end_chain.next #=> "the"
Contributing
 Fork it ( https://github.com/mccallofthewild/markov/fork )
 Create your feature branch (git checkout b mynewfeature)
 Commit your changes (git commit am 'Add some feature')
 Push to the branch (git push origin mynewfeature)
 Create a new Pull Request
Contributors
 McCall Alexander mccallofthewild  creator, maintainer